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	Author	Aierken, Y.; Çakır, D.; Sevik, C.; Peeters, F.M.
	Title	Thermal properties of black and blue phosphorenes from a first-principles quasiharmonic approach			Type	A1 Journal article
	Year	2015	Publication	Physical review : B : condensed matter and materials physics	Abbreviated Journal	Phys Rev B
	Volume	92	Issue	92	Pages	081408
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Different allotropes of phosphorene are possible of which black and blue phosphorus are the most stable. While blue phosphorus has isotropic properties, black phosphorus is strongly anisotropic in its electronic and optical properties due to its anisotropic crystal structure. In this work, we systematically investigated the lattice thermal properties of black and blue phosphorene by using first-principles calculations based on the quasiharmonic approximation approach. Similar to the optoelectronic and electronic properties, we predict that black phosphorene has highly anisotropic thermal properties, in contrast to the blue phase. The linear thermal expansion coefficients along the zigzag and armchair direction differ up to 20% in black phosphorene. The armchair direction of black phosphorene is more expandable as compared to the zigzag direction and the biaxial expansion of blue phosphorene under finite temperature. Our comparative analysis reveals that the inclusion of finite-temperature effects makes the blue phase thermodynamically more stable over the black phase above 135 K.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000359860700005	Publication Date	2015-08-19
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1098-0121	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.836	Times cited	124	Open Access
	Notes	This work was supported by the Flemish Science Founda- tion (FWO-Vl) and the Methusalem foundation of the Flem- ish government. Computational resources were provided by TUBITAK ULAKBIM, High Performance and Grid Comput- ing Center (TR-Grid e-Infrastructure), and HPC infrastructure of the University of Antwerp (CalcUA), a division of the Flemish Supercomputer Center (VSC), which is funded by the Hercules foundation. C.S. acknowledges the support from Anadolu University (BAP-1407F335), and Turkish Academy of Sciences (TUBA-GEBIP).			Approved	Most recent IF: 3.836; 2015 IF: 3.736
	Call Number	c:irua:127754			Serial	4034
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	Author	Alyörük, M.M.; Aierken, Y.; Çakır, D.; Peeters, F.M.; Sevik, C.
	Title	Promising Piezoelectric Performance of Single Layer Transition-Metal Dichalcogenides and Dioxides			Type	A1 Journal article
	Year	2015	Publication	The journal of physical chemistry: C : nanomaterials and interfaces	Abbreviated Journal	J Phys Chem C
	Volume	119	Issue	119	Pages	23231-23237
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	Piezoelectricity is a unique material property that allows one to convert mechanical energy into electrical one or vice versa. Transition metal dichalcogenides (TMDC) and transition metal dioxides (TMDO) are expected to have great potential for piezoelectric device applications due to their noncentrosymmetric and two-dimensional crystal structure. A detailed theoretical investigation of the piezoelectric stress (e 11 ) and piezoelectric strain (d 11 ) coefficients of single layer TMDCs and TMDOs with chemical formula MX 2 (where M= Cr, Mo, W, Ti, Zr, Hf, Sn and X = O, S, Se, Te) is presented by using first-principles calculations based on density func- tional theory. We predict that not only the Mo- and W-based members of this family but also the other materials with M= Cr, Ti, Zr and Sn exhibit highly promising piezoelectric properties. CrTe 2 has the largest e 11 and d 11 coefficients among the group VI elements (i.e., Cr, Mo, and W). In addition, the relaxed-ion e 11 and d 11 coefficients of SnS 2 are almost the same as those of CrTe 2 . Furthermore, TiO 2 and ZrO 2 pose comparable or even larger e 11 coefficients as compared to Mo- and W-based TMDCs and TMDOs. Our calculations reveal that TMDC and TMDO structures are strong candidates for future atomically thin piezoelectric applications such as transducers, sensors, and energy harvesting devices due to their piezoelectric coefficients that are comparable (even larger) to currently used bulk piezoelectric materials.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000362702100054	Publication Date	2015-09-14
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1932-7447	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	4.536	Times cited	134	Open Access
	Notes	M.M.A and C.S. acknowledges the support from Scientific and Technological Research Council of Turkey (TUBITAK- 113F333). C.S. acknowledges support from Anadolu University (BAP-1407F335, -1505F200), and Turkish Academy of Sciences (TUBA-GEBIP). Computational resources were provided by TUBITAK ULAKBIM, High Performance and Grid Computing Center (TR-Grid e-Infrastructure), and HPC infrastructure of the University of Antwerp (CalcUA) a division of the Flemish Supercomputer Center (VSC), which is funded by the Hercules foundation.			Approved	Most recent IF: 4.536; 2015 IF: 4.772
	Call Number	c:irua:129418			Serial	4035
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	Author	Sevik, C.; Bekaert, J.; Petrov, M.; Milošević, M.V.
	Title	High-temperature multigap superconductivity in two-dimensional metal borides			Type	A1 Journal article
	Year	2022	Publication	Physical review materials	Abbreviated Journal	Phys. Rev. Materials
	Volume	6	Issue	2	Pages	024803
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000766666300003	Publication Date	2022-02-28
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2475-9953	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.4	Times cited	4	Open Access	Not_Open_Access
	Notes	Universiteit Antwerpen; Türkiye Bilimsel ve Teknolojik Araştirma Kurumu, COST-118F187 ; Air Force Office of Scientific Research, FA9550-19-1-7048 ; Fonds Wetenschappelijk Onderzoek;			Approved	Most recent IF: 3.4
	Call Number	CMT @ cmt @c:irua:187126			Serial	7047
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	Author	Demiroglu, I.; Peeters, F.M.; Gulseren, O.; Cakir, D.; Sevik, C.
	Title	Alkali metal intercalation in MXene/graphene heterostructures : a new platform for ion battery applications			Type	A1 Journal article
	Year	2019	Publication	The journal of physical chemistry letters	Abbreviated Journal	J Phys Chem Lett
	Volume	10	Issue	4	Pages	727-734
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	The adsorption and diffusion of Na, K, and Ca atoms on MXene/graphene heterostructures of MXene systems Sc2C(OH)(2), Ti2CO2, and V2CO2 are systematically investigated by using first-principles methods. We found that alkali metal intercalation is energetically favorable and thermally stable for Ti2CO2/graphene and V2CO2/graphene heterostructures but not for Sc2C(OH)(2). Diffusion kinetics calculations showed the advantage of MXene/graphene heterostructures over sole MXene systems as the energy barriers are halved for the considered alkali metals. Low energy barriers are found for Na and K ions, which are promising for fast charge/discharge rates. Calculated voltage profiles reveal that estimated high capacities can be fully achieved for Na ion in V2CO2/graphene and Ti2CO2/graphene heterostructures. Our results indicate that Ti2CO2/graphene and V2CO2/graphene electrode materials are very promising for Na ion battery applications. The former could be exploited for low voltage applications while the latter will be more appropriate for higher voltages.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000459948800005	Publication Date	2019-01-30
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1948-7185	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	9.353	Times cited	67	Open Access
	Notes	; We acknowledge the support from the TUBITAK (116F080) and the BAGEP Award of the Science Academy. Part of this work was supported by the FLAG -ERA project TRANS-2D-TMD. A part of this work was supported by University of North Dakota Early Career Award (Grant number: 20622-4000-02624). We also acknowledge financial support from ND EPSCoR through NSF grant OIA-1355466. Computational resources were provided by the High Performance and Grid Computing Center (TRGrid e-Infrastructure) of TUBITAK ULAKBIM, the National Center for High Performance Computing (UHeM) of Istanbul Technical University, and Computational Research Center (HPC Linux cluster) at the University of North Dakota. This work was performed, in part, at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, and supported by the U.S. Department of Energy, Office of Science, under contract no. DE-AC02-06CH11357. ;			Approved	Most recent IF: 9.353
	Call Number	UA @ admin @ c:irua:158618			Serial	5194
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	Author	Yagmurcukardes, M.; Sevik, C.; Peeters, F.M.
	Title	Electronic, vibrational, elastic, and piezoelectric properties of monolayer Janus MoSTe phases: A first-principles study			Type	A1 Journal article
	Year	2019	Publication	Physical review B	Abbreviated Journal	Phys Rev B
	Volume	100	Issue	4	Pages	045415
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	By performing density functional theory based first-principles calculations, the electronic, vibrational, elastic, and piezoelectric properties of two dynamically stable crystal phases of monolayer Janus MoSTe, namely 1H-MoSTe and 1T'-MoSTe, are investigated. Vibrational frequency analysis reveals that the other possible crystal structure, 1T-MoSTe, of this Janus monolayer does not exhibit dynamical stability. The 1H-MoSTe phase is found to be an indirect band-gap semiconductor while 1T'-MoSTe is predicted as small-gap semiconductor. Notably, in contrast to the direct band-gap nature of monolayers 1H-MoS2 and 1H-MoTe2, 1H-MoSTe is found to be an indirect gap semiconductor driven by the induced surface strains on each side of the structure. The calculated Raman spectrum of each structure shows unique character enabling us to clearly distinguish the stable crystal phases via Raman measurements. The systematic piezoelectric stress and strain coefficient analysis reveals that out-of-plane piezoelectricity appears in 1H-MoSTe and the noncentral symmetric 1T'-MoSTe has large piezoelectric coefficients. Static total-energy calculations show clearly that the formation of 1T'-MoSTe is feasible by using 1T'-MoTe2 as a basis monolayer. Therefore, we propose that the Janus MoSTe structure can be fabricated in two dynamically stable phases which possess unique electronic, dynamical, and piezoelectric properties.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000476687800003	Publication Date	2019-07-19
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2469-9969; 2469-9950	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.836	Times cited	91	Open Access
	Notes	; Computational resources were provided by TUBITAK ULAKBIM, High Performance and Grid Computing Center (TR-Grid e-Infrastructure). This work was supported by the Flemish Science Foundation (FWO-Vl) by a postdoctoral fellowship (M.Y.). ;			Approved	Most recent IF: 3.836
	Call Number	UA @ admin @ c:irua:161899			Serial	5411
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	Author	Bekaert, J.; Sevik, C.; Milošević, M.V.
	Title	First-principles exploration of superconductivity in MXenes			Type	A1 Journal article
	Year	2020	Publication	Nanoscale	Abbreviated Journal	Nanoscale
	Volume	12	Issue		Pages	17354-17361
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	MXenes are an emerging class of two-dimensional materials, which in their thinnest limit consist of a monolayer of carbon or nitrogen (X) sandwiched between two transition metal (M) layers. We have systematically searched for superconductivity among MXenes for a range of transition metal elements, based on a full first-principles characterization in combination with the Eliashberg formalism. Thus, we identified six superconducting MXenes: three carbides (Mo2C, W2C and Sc2C) and three nitrides (Mo2N, W2N and Ta2N). The highest critical temperature of similar to 16 K is found in Mo2N, for which a successful synthesis method has been established [Urbankowskiet al.,Nanoscale, 2017,9, 17722-17730]. Moreover, W2N presents a novel case of competing superconducting and charge density wave phases.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000563481700017	Publication Date	2020-08-07
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2040-3364	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	6.7	Times cited	15	Open Access
	Notes	; This work is supported by The Scientific and Technological Research Council of Turkey (TUBITAK) under the contract number COST-118F187, the Air Force Office of Scientific Research under award number FA9550-19-1-7048, by Research Foundation-Flanders (FWO) and the University of Antwerp (BOF). The collaboration was fostered by COST action NANOCOHYBRI (CA16218). Computational resources were provided by the High Performance and Grid Computing Center (TRGrid e-Infrastructure) of TUBITAK ULAKBIM, the National Center for High Performance Computing (UHeM) of Istanbul Technical University, and by the VSC (Flemish Supercomputer Center), funded by the FWO and the Flemish Government – department EWI. J. B. acknowledges support of a postdoctoral fellowship of the FWO. ;			Approved	Most recent IF: 6.7; 2020 IF: 7.367
	Call Number	UA @ admin @ c:irua:171988			Serial	6521
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	Author	Siriwardane, E.M.D.; Demiroglu, I.; Sevik, C.; Peeters, F.M.; Çakir, D.
	Title	Assessment of sulfur-functionalized MXenes for li-ion battery applications			Type	A1 Journal article
	Year	2020	Publication	Journal Of Physical Chemistry C	Abbreviated Journal	J Phys Chem C
	Volume	124	Issue	39	Pages	21293-21304
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	The surface termination of MXenes greatly determines the electrochemical properties and ion kinetics on their surfaces. So far, hydroxyl-, oxygen-, and fluorine-terminated MXenes have been widely studied for energy storage applications. Recently, sulfur-functionalized MXene structures, which possess low diffusion barriers, have been proposed as candidate materials to enhance battery performance. We performed first-principles calculations on the structural, stability, electrochemical, and ion dynamic properties of Li-adsorbed sulfur-functionalized groups 3B, 4B, 5B, and 6B transition-metal (M)-based MXenes (i.e., M2CS2 with M = Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W). We performed phonon calculations, which indicated that all of the above M2CS2 MXenes, except for Sc, are dynamically stable at T = 0 K. The ground-state structure of each M2CS2 monolayer depends on the type of M atom. For instance, while sulfur prefers to sit at the FCC site on Ti2CS2, it occupies the HCP site of Cr-based MXene. We determined the Li adsorption configurations at different concentrations using the cluster expansion method. The highest maximum open-circuit voltages were computed for the group 4B element (i.e., Ti, Zr, and Hf)-based M2CS2, which are larger than 2.1 V, while their average voltages are approximately 1 V. The maximum voltage for the group 6B element (i.e., Cr, Mo, W)-based M2CS2 is less than 1 V, and the average voltage is less than 0.71 V. We found that S functionalization is helpful for capacity improvements over the O-terminated MXenes. In this respect, the computed storage gravimetric capacity may reach up to 417.4 mAh/g for Ti2CS2 and 404.5 mAh/g for V2CS2. Ta-, Cr-, Mo-, and W-based M2CS2 MXenes show very low capacities, which are less than 100 mAh/g. The Li surface diffusion energy barriers for all of the considered MXenes are less than 0.22 eV, which is favorable for high charging and discharging rates. Finally, ab initio molecular dynamic simulations performed at 400 K and bond-length analysis with respect to Li concentration verify that selected promising systems are robust against thermally induced perturbations that may induce structural transformations or distortions and undesirable Li release.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000577151900008	Publication Date	2020-09-01
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1932-7447; 1932-7455	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.7	Times cited	15	Open Access
	Notes	; Computational resources were provided by the HPC infrastructure of the University of Antwerp (CalcUA), a division of the Flemish Supercomputer Center (VSC), which is funded by the Hercules Foundation. This work was supported, in part, by The Scientific and Technological Research Council of Turkey (TUBITAK) under contract no. 118F512 and the Air Force Office of Scientific Research under award no. FA9550-19-1-7048. This work was performed in part at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357. This work was supported, in part, by The Scientific and Technological Research Council of Turkey (TUBITAK) under contract no. 118C026. ;			Approved	Most recent IF: 3.7; 2020 IF: 4.536
	Call Number	UA @ admin @ c:irua:172693			Serial	6452
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	Author	Demiroglu, I.; Sevik, C.
	Title	Extraordinary negative thermal expansion of two-dimensional nitrides : a comparative ab initio study of quasiharmonic approximation and molecular dynamics simulations			Type	A1 Journal article
	Year	2021	Publication	Physical Review B	Abbreviated Journal	Phys Rev B
	Volume	103	Issue	8	Pages	085430
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Thermal expansion behavior of two-dimensional (2D) nitrides and graphene were studied by ab initio molecular dynamics (MD) simulations as well as quasiharmonic approximation (QHA). Anharmonicity of the acoustic phonon modes are related to the unusual negative thermal expansion (NTE) behavior of the nitrides. Our results also hint that direct ab initio MD simulations are a more elaborate method to investigate thermal expansion behavior of 2D materials than the QHA. Nevertheless, giant NTE coefficients are found for h-GaN and h-AlN within the covered temperature range 100-600 K regardless of the chosen computational method. This unusual NTE of 2D nitrides is reasoned with the out-of-plane oscillations related to the rippling behavior of the monolayers.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000620346100007	Publication Date	2021-02-22
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2469-9969; 2469-9950	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.836	Times cited		Open Access	OpenAccess
	Notes				Approved	Most recent IF: 3.836
	Call Number	UA @ admin @ c:irua:176671			Serial	7956
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	Author	Saiz, F.; Karaaslan, Y.; Rurali, R.; Sevik, C.
	Title	Interatomic potential for predicting the thermal conductivity of zirconium trisulfide monolayers with molecular dynamics			Type	A1 Journal article
	Year	2021	Publication	Journal Of Applied Physics	Abbreviated Journal	J Appl Phys
	Volume	129	Issue	15	Pages	155105
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	We present here a new interatomic potential parameter set to predict the thermal conductivity of zirconium trisulfide monolayers. The generated Tersoff-type force field is parameterized using data collected with first-principles calculations. We use non-equilibrium molecular dynamics simulations to predict the thermal conductivity. The generated parameters result in very good agreement in structural, mechanical, and dynamical parameters. The room temperature lattice thermal conductivity ( kappa) of the considered crystal is predicted to be kappa x x = 25.69Wm – 1K – 1 and kappa y y = 42.38Wm – 1K – 1, which both agree well with their corresponding first-principles values with a discrepancy of less than 5%. Moreover, the calculated kappa variation with temperature (200 and 400 K) are comparable within the framework of the accuracy of both first-principles and molecular dynamics simulations.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000641993600001	Publication Date	2021-04-19
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0021-8979; 1089-7550	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	2.068	Times cited		Open Access	OpenAccess
	Notes				Approved	Most recent IF: 2.068
	Call Number	UA @ admin @ c:irua:178234			Serial	8112
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	Author	Korkmaz, Y.A.; Bulutay, C.; Sevik, C.
	Title	k · p parametrization and linear and circular dichroism in strained monolayer (Janus) transition metal dichalcogenides from first-principles			Type	A1 Journal article
	Year	2021	Publication	Journal Of Physical Chemistry C	Abbreviated Journal	J Phys Chem C
	Volume	125	Issue	13	Pages	7439-7450
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	Semiconductor monolayer transition metal dichalcogenides (TMDs) have brought a new paradigm by introducing optically addressable valley degree of freedom. Concomitantly, their high flexibility constitutes a unique platform that links optics to mechanics via valleytronics. With the intention to expedite the research in this direction, we investigated ten TMDs, namely MoS2, MoSe2, MoTe2, WS2, WSe2, WTe2, MoSSe, MoSeTe, WSSe, and WSeTe, which particularly includes their so-called janus types (JTMDs). First, we obtained their electronic band structures using regular and hybrid density functional theory (DFT) calculations in the presence of the spin-orbit coupling and biaxial or uniaxial strain. Our DFT results indicated that against the expectations based on their reported piezoelectric behavior, JTMDs typically interpolated between the standard band properties of the constituent TMDs without producing a novel feature. Next, by fitting to our DFT data we generated both spinless and spinful k center dot p parameter sets which are quite accurate over the K valley where the optical activity occurs. As an important application of this parametrization, we considered the circular and linear dichroism under strain. Among the studied (J)TMDs, WTe2 stood out with its largest linear dichroism under uniaxial strain because of its narrower band gap and large K valley uniaxial deformation potential. This led us to suggest WTe2 monolayer membranes for optical polarization-based strain measurements, or conversely, as strain tunable optical polarizers.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000639044400045	Publication Date	2021-03-26
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1932-7447; 1932-7455	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	4.536	Times cited		Open Access	OpenAccess
	Notes				Approved	Most recent IF: 4.536
	Call Number	UA @ admin @ c:irua:178264			Serial	8136
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	Author	Demiroglu, I.; Karaaslan, Y.; Kocabas, T.; Keceli, M.; Vazquez-Mayagoitia, A.; Sevik, C.
	Title	Computation of the thermal expansion coefficient of graphene with Gaussian approximation potentials			Type	A1 Journal article
	Year	2021	Publication	Journal Of Physical Chemistry C	Abbreviated Journal	J Phys Chem C
	Volume	125	Issue	26	Pages	14409-14415
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	Direct experimental measurement of thermal expansion coefficient without substrate effects is a challenging task for two-dimensional (2D) materials, and its accurate estimation with large-scale ab initio molecular dynamics is computationally very expensive. Machine learning-based interatomic potentials trained with ab initio data have been successfully used in molecular dynamics simulations to decrease the computational cost without compromising the accuracy. In this study, we investigated using Gaussian approximation potentials to reproduce the density functional theory-level accuracy for graphene within both lattice dynamical and molecular dynamical methods, and to extend their applicability to larger length and time scales. Two such potentials are considered, GAP17 and GAP20. GAP17, which was trained with pristine graphene structures, is found to give closer results to density functional theory calculations at different scales. Further vibrational and structural analyses verify that the same conclusions can be deduced with density functional theory level in terms of the reasoning of the thermal expansion behavior, and the negative thermal expansion behavior is associated with long-range out-of-plane phonon vibrations. Thus, it is argued that the enabled larger system sizes by machine learning potentials may even enhance the accuracy compared to small-size-limited ab initio molecular dynamics.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000672734100027	Publication Date	2021-06-24
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1932-7447; 1932-7455	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	4.536	Times cited		Open Access	OpenAccess
	Notes				Approved	Most recent IF: 4.536
	Call Number	UA @ admin @ c:irua:179850			Serial	7719
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	Author	Karaaslan, Y.; Haskins, J.B.; Yapicioglu, H.; Sevik, C.
	Title	Influence of randomly distributed vacancy defects on thermal transport in two-dimensional group-III nitrides			Type	A1 Journal article
	Year	2021	Publication	Journal Of Applied Physics	Abbreviated Journal	J Appl Phys
	Volume	129	Issue	22	Pages	224304
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Efficient thermal transport control is a fundamental issue for electronic device applications such as information, communication, and energy storage technologies in modern electronics in order to achieve desired thermal conditions. Structural defects in materials provide a mechanism to adjust the thermal transport properties of these materials on demand. In this context, the effect of structural defects on lattice thermal conductivities of two-dimensional hexagonal binary group-III nitride (XN, X = B, Al, and Ga) semiconductors is systematically investigated by means of classical molecular dynamics simulations performed with recently developed transferable inter-atomic potentials accurately describing defect energies. Here, two different Green-Kubo based approaches and another approach based on non-equilibrium molecular dynamics are compared in order to get an overall understanding. Our investigation clearly shows that defect concentrations of 3% decrease the thermal conductivity of systems containing these nitrites up to 95%. Results hint that structural defects can be used as effective adjustment parameters in controlling thermal transport properties in device applications associated with these materials. Published under an exclusive license by AIP Publishing.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000692024300001	Publication Date	2021-06-09
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0021-8979; 1089-7550	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	2.068	Times cited		Open Access	Not_Open_Access
	Notes				Approved	Most recent IF: 2.068
	Call Number	UA @ admin @ c:irua:181618			Serial	8096
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	Author	Sun, J.; Li, Y.; Karaaslan, Y.; Sevik, C.; Chen, Y.
	Title	Misfit dislocation structure and thermal boundary conductance of GaN/AlN interfaces			Type	A1 Journal article
	Year	2021	Publication	Journal Of Applied Physics	Abbreviated Journal	J Appl Phys
	Volume	130	Issue	3	Pages	035301
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	The structure and thermal boundary conductance of the wurtzite GaN/AlN (0001) interface are investigated using molecular dynamics simulation. Simulation results with three different empirical interatomic potentials have produced similar misfit dislocation networks and dislocation core structures. Specifically, the misfit dislocation network at the GaN/AlN interface is found to consist of pure edge dislocations with a Burgers vector of 1/3(1 (2) over bar 10) and the misfit dislocation core has an eight-atom ring structure. Although different interatomic potentials lead to different dislocation properties and thermal conductance values, all have demonstrated a significant effect of misfit dislocations on the thermal boundary conductance of the GaN/AlN (0001) interface. Published under an exclusive license by AIP Publishing.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000694725800001	Publication Date	2021-07-15
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0021-8979; 1089-7550	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	2.068	Times cited		Open Access	Not_Open_Access
	Notes				Approved	Most recent IF: 2.068
	Call Number	UA @ admin @ c:irua:181623			Serial	8254
Permanent link to this record



	Author	Demirkol, Ö.; Sevik, C.; Demiroğlu, I.
	Title	First principles assessment of the phase stability and transition mechanisms of designated crystal structures of pristine and Janus transition metal dichalcogenides			Type	A1 Journal article
	Year	2022	Publication	Physical chemistry, chemical physics	Abbreviated Journal	Phys Chem Chem Phys
	Volume	24	Issue	12	Pages	7430-7441
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Two-dimensional Transition Metal Dichalcogenides (TMDs) possessing extraordinary physical properties at reduced dimensionality have attracted interest due to their promise in electronic and optical device applications. However, TMD monolayers can show a broad range of different properties depending on their crystal phase; for example, H phases are usually semiconductors, while the T phases are metallic. Thus, controlling phase transitions has become critical for device applications. In this study, the energetically low-lying crystal structures of pristine and Janus TMDs are investigated by using ab initio Nudged Elastic Band and molecular dynamics simulations to provide a general explanation for their phase stability and transition properties. Across all materials investigated, the T phase is found to be the least stable and the H phase is the most stable except for WTe2, while the T' and T '' phases change places according to the TMD material. The transition energy barriers are found to be large enough to hint that even the higher energy phases are unlikely to undergo a phase transition to a more stable phase if they can be achieved except for the least stable T phase, which has zero barrier towards the T ' phase. Indeed, in molecular dynamics simulations the thermodynamically least stable T phase transformed into the T ' phase spontaneously while in general no other phase transition was observed up to 2100 K for the other three phases. Thus, the examined T ', T '' and H phases were shown to be mostly stable and do not readily transform into another phase. Furthermore, so-called mixed phase calculations considered in our study explain the experimentally observed lateral hybrid structures and point out that the coexistence of different phases is strongly stable against phase transitions. Indeed, stable complex structures such as metal-semiconductor-metal architectures, which have immense potential to be used in future device applications, are also possible based on our investigation.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000766791000001	Publication Date	2022-02-23
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1463-9076; 1463-9084	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.3	Times cited		Open Access	OpenAccess
	Notes				Approved	Most recent IF: 3.3
	Call Number	UA @ admin @ c:irua:187184			Serial	7164
Permanent link to this record



	Author	Bekaert, J.; Sevik, C.; Milošević, M.V.
	Title	Enhancing superconductivity in MXenes through hydrogenation			Type	A1 Journal article
	Year	2022	Publication	Nanoscale	Abbreviated Journal	Nanoscale
	Volume	14	Issue	27	Pages	9918-9924
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	Two-dimensional transition metal carbides and nitrides (MXenes) are an emerging class of atomically-thin superconductors, whose characteristics are highly prone to tailoring by surface functionalization. Here we explore the use of hydrogen adatoms to enhance phonon-mediated superconductivity in MXenes, based on first-principles calculations combined with Eliashberg theory. We first demonstrate the stability of three different structural models of hydrogenated Mo- and W-based MXenes. Particularly high critical temperatures of over 30 K are obtained for hydrogenated Mo2N and W2N. Several mechanisms responsible for the enhanced electron-phonon coupling are uncovered, namely (i) hydrogen-induced changes in the phonon spectrum of the host MXene, (ii) emerging hydrogen-based phonon modes, and (iii) charge transfer from hydrogen to the MXene layer, boosting the density of states at the Fermi level. Finally, we demonstrate that hydrogen adatoms are moreover able to induce superconductivity in MXenes that are not superconducting in pristine form, such as Nb2C.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000820350600001	Publication Date	2022-06-27
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2040-3364; 2040-3372	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	6.7	Times cited	2	Open Access	OpenAccess
	Notes				Approved	Most recent IF: 6.7
	Call Number	UA @ admin @ c:irua:189580			Serial	7155
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	Author	Seyedmohammadzadeh, M.; Sevik, C.; Guelseren, O.
	Title	Two-dimensional heterostructures formed by graphenelike ZnO and MgO monolayers for optoelectronic applications			Type	A1 Journal article
	Year	2022	Publication	Physical review materials	Abbreviated Journal
	Volume	6	Issue	10	Pages	104004-104013
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Two-dimensional heterostructures are an emerging class of materials for novel applications because of extensive engineering potential by tailoring intriguing properties of different layers as well as the ones arising from their interface. A systematic investigation of mechanical, electronic, and optical properties of possible heterostructures formed by bilayer structures graphenelike ZnO and MgO monolayers is presented. Different functionality of each layer makes these heterostructures very appealing for device applications. ZnO layer is convenient for electron transport in these structures, while MgO layer improves electron collection. At the outset, all of the four possible stacking configurations across the heterostructure are mechanically stable. In addition, stability analysis using phonon dispersion reveals that the AB stacking formed by placing the Mg atom on top of the O atom of the ZnO layer is also dynamically stable at zero temperature. Henceforth, we have investigated the optical properties of these stable heterostructures by applying many-body perturbation theory within the framework of GW approximation and solving the Bethe-Salpeter equation. It is demonstrated that strong excitonic effects reduce the optical band gap to the visible light spectrum range. These results show that this new two-dimensional form of ZnO/MgO heterostructures open an avenue for novel optoelectronic device applications.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000877514900005	Publication Date	2022-10-24
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2475-9953	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.4	Times cited		Open Access	OpenAccess
	Notes				Approved	Most recent IF: 3.4
	Call Number	UA @ admin @ c:irua:192167			Serial	7346
Permanent link to this record



	Author	Yorulmaz, U.; Šabani, D.; Yagmurcukardes, M.; Sevik, C.; Milošević, M.V.
	Title	High-throughput analysis of tetragonal transition metal Xenes			Type	A1 Journal article
	Year	2022	Publication	Physical chemistry, chemical physics	Abbreviated Journal	Phys Chem Chem Phys
	Volume	24	Issue	48	Pages	29406-29412
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	We report a high-throughput first-principles characterization of the structural, mechanical, electronic, and vibrational properties of tetragonal single-layer transition metal Xenes (t-TMXs). Our calculations revealed 22 dynamically, mechanically and chemically stable structures among the 96 possible free-standing layers present in the t-TMX family. As a fingerprint for their structural identification, we identified four characteristic Raman active phonon modes, namely three in-plane and one out-of-plane optical branches, with various intensities and frequencies depending on the material in question. Spin-polarized electronic calculations demonstrated that anti-ferromagnetic (AFM) metals, ferromagnetic (FM) metals, AFM semiconductors, and non-magnetic semiconductor materials exist within this family, evidencing the potential of t-TMXs for further use in multifunctional heterostructures.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000892446100001	Publication Date	2022-11-30
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1463-9076; 1463-9084	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.3	Times cited	1	Open Access	Not_Open_Access
	Notes				Approved	Most recent IF: 3.3
	Call Number	UA @ admin @ c:irua:192762			Serial	7310
Permanent link to this record



	Author	Duden, E.I.; Savaci, U.; Turan, S.; Sevik, C.; Demiroglu, I.
	Title	Intercalation of argon in honeycomb structures towards promising strategy for rechargeable Li-ion batteries			Type	A1 Journal article
	Year	2023	Publication	Journal of physics : condensed matter	Abbreviated Journal
	Volume	35	Issue	8	Pages	085301-85311
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	High-performance rechargeable batteries are becoming very important for high-end technologies with their ever increasing application areas. Hence, improving the performance of such batteries has become the main bottleneck to transferring high-end technologies to end users. In this study, we propose an argon intercalation strategy to enhance battery performance via engineering the interlayer spacing of honeycomb structures such as graphite, a common electrode material in lithium-ion batteries (LIBs). Herein, we systematically investigated the LIB performance of graphite and hexagonal boron nitride (h-BN) when argon atoms were sent into between their layers by using first-principles density-functional-theory calculations. Our results showed enhanced lithium binding for graphite and h-BN structures when argon atoms were intercalated. The increased interlayer space doubles the gravimetric lithium capacity for graphite, while the volumetric capacity also increased by around 20% even though the volume was also increased. The ab initio molecular dynamics simulations indicate the thermal stability of such graphite structures against any structural transformation and Li release. The nudged-elastic-band calculations showed that the migration energy barriers were drastically lowered, which promises fast charging capability for batteries containing graphite electrodes. Although a similar level of battery promise was not achieved for h-BN material, its enhanced battery capabilities by argon intercalation also support that the argon intercalation strategy can be a viable route to enhance such honeycomb battery electrodes.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000899825400001	Publication Date	2022-12-05
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0953-8984	ISBN		Additional Links	UA library record; WoS full record
	Impact Factor	2.7	Times cited		Open Access	OpenAccess
	Notes				Approved	Most recent IF: 2.7; 2023 IF: 2.649
	Call Number	UA @ admin @ c:irua:193399			Serial	7313
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	Author	Yorulmaz, U.; Demiroglu, I.; Cakir, D.; Gulseren, O.; Sevik, C.
	Title	A systematicalab-initioreview of promising 2D MXene monolayers towards Li-ion battery applications			Type	A1 Journal article
	Year	2020	Publication	JPhys Energy	Abbreviated Journal
	Volume	2	Issue	3	Pages	032006
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	Two-dimensional materials have been attracting increasing interests because of their outstanding properties for Lithium-ion battery applications. In particular, a material family called MXenes (Mn+1Cn, where n = 1, 2, 3) have been recently attracted immense interest in this respect due to their incomparable fast-charging properties and high capacity promises. In this article, we review the state-of-the-art computational progress on Li-ion battery applications of MXene materials in accordance with our systematical DFT calculations. Structural, mechanical, dynamical, and electrical properties of 20 distinct MXene (M: Sc, Ti, V, Cr, Nb, Mo, Hf, Ta, W, and Zr) have been discussed. The battery performances of these MXene monolayers are further investigated by Li-ion binding energies, open circuit voltage values, and Li migration energy barriers. The experimental and theoretical progress up to date demonstrates particularly the potential of non-terminated or pristine MXene materials in Li ion-storage applications. Stability analyses show most of the pristine MXenes should be achievable, however susceptible to the development progress on the experimental growth procedures. Among pristine MXenes, Ti2C, V2C, Sc2C, and Zr2C compounds excel with their high charge/discharge rate prospect due to their extremely low Li diffusion energy barriers. Considering also their higher predicted gravimetric capacities, Sc, Ti, V, and Zr containing MXenes are more promising for their utilization in energy storage applications.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000569868600001	Publication Date	2020-07-16
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2515-7655	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	6.9	Times cited		Open Access
	Notes				Approved	Most recent IF: 6.9; 2020 IF: NA
	Call Number	UA @ admin @ c:irua:193748			Serial	7399
Permanent link to this record



	Author	Sevik, C.; Çakir, D.
	Title	Tailoring Storage Capacity and Ion Kinetics in Ti2CO2/Graphene Heterostructures by Functionalization of Graphene			Type	A1 Journal article
	Year	2019	Publication	Physical review applied	Abbreviated Journal
	Volume	12	Issue	1	Pages	014001
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Using first-principles calculations, we evaluate the electrochemical performance of heterostructures made up of Ti2CO2 and chemically modified graphene for Li batteries. We find that heteroatom doping and molecule intercalation have a significant impact on the storage capacity and Li migration barrier energies. While N and S doping do not improve the storage capacity, B doping together with molecule interaction make it possible to intercalate two layers of Li, which stick separately to the surface of Ti2CO2 and B-doped graphene. The calculated diffusion-barrier energies (E-diff), which are between 0.3 and 0.4 eV depending on Li concentration, are quite promising for fast charge and discharge rates. Besides, the predicted E-diff as much as 2 eV for the diffusion of the Li atom from the Ti2CO2 surface to the B-doped graphene surface significantly suppresses the interlayer Li migration, which diminishes the charge and discharge rates. The calculated volume and lattice parameter changes indicate that Ti2CO2/graphene hybrid structures exhibit cyclic stability against Li loading and unloading. Consequently, first-principles calculations we perform evidently highlight the favorable effect of molecular intercalation on the capacity improvement of ion batteries.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000473312000001	Publication Date	2019-07-01
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2331-7019	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor		Times cited		Open Access
	Notes				Approved	no
	Call Number	UA @ admin @ c:irua:193755			Serial	8640
Permanent link to this record



	Author	Siriwardane, E.M.D.; Demiroglu, I.; Sevik, C.; Cakir, D.
	Title	Achieving Fast Kinetics and Enhanced Li Storage Capacity for Ti3C2O2 by Intercalation of Quinone Molecules			Type	A1 Journal article
	Year	2019	Publication	ACS applied energy materials	Abbreviated Journal
	Volume	2	Issue	2	Pages	1251-1258
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	Using first-principles calculations, we demonstrated that high lithium storage capacity and fast kinetics are achieved for Ti3C2O2 by preintercalating organic molecules. As a proof-of-concept, two different quinone molecules, namely 1,4-benzoquinone (C6H4O2) and tetrafluoro-1,4-benzoquinone (C6F4O2) were selected as the molecular linkers to demonstrate the feasibility of this interlayer engineering strategy for energy storage. As compared to Ti3C2O2 bilayer without linker molecules, our pillared structures facilitate a much faster ion transport, promising a higher charge/discharge rate for Li. For example, while the diffusion barrier of a single Li ion within pristine Ti3C2O2 bilayer is at least 1.0 eV, it becomes 0.3 eV in pillared structures, which is comparable and even lower than that of commercial materials. At high Li concentrations, the calculated diffusion barriers are as low as 0.4 eV. Out-of-plane migration of Li ions is hindered due to large barrier energy with a value of around 1-1.35 eV. Concerning storage capacity, we can only intercalate one monolayer of Li within pristine Ti3C2O2 bilayer. In contrast, pillared structures offer significantly higher storage capacity. Our calculations showed that at least two layers of Li can be intercalated between Ti3C2O2 layers without forming bulk Li and losing the pillared structure upon Li loading/unloading. A small change in the in-plane lattice parameters (<0.5%) and volume (<1.0%) and ab initio molecular dynamics simulations prove the stability of the pillared structures against Li intercalation and thermal effects. Intercalated molecules avoid the large contraction/expansion of the whole structure, which is one of the key problems in electrochemical energy storage. Pillared structures allow us to realize electrodes with high capacity and fast kinetics. Our results open new research paths for improving the performance of not only MXenes but also other layered materials for supercapacitor and battery applications.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000459948900037	Publication Date	2019-01-04
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2574-0962	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor		Times cited		Open Access
	Notes				Approved	no
	Call Number	UA @ admin @ c:irua:193759			Serial	7414
Permanent link to this record



	Author	Kocabas, T.; Cakir, D.; Sevik, C.
	Title	First-principles discovery of stable two-dimensional materials with high-level piezoelectric response			Type	A1 Journal article
	Year	2021	Publication	Journal Of Physics-Condensed Matter	Abbreviated Journal	J Phys-Condens Mat
	Volume	33	Issue	11	Pages	115705
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	The rational design of two-dimensional (2D) piezoelectric materials has recently garnered great interest due to their increasing use in technological applications, including sensor technology, actuating devices, energy harvesting, and medical applications. Several materials possessing high piezoelectric response have been reported so far, but a high-throughput first-principles approach to estimate the piezoelectric potential of layered materials has not been performed yet. In this study, we systematically investigated the piezoelectric (e(11), d(11)) and elastic (C-11 and C-12) properties of 128 thermodynamically stable 2D semiconductor materials by employing first-principle methods. Our high-throughput approach demonstrates that the materials containing Group-V elements produce significantly high piezoelectric strain constants, d(11) > 40 pm V-1, and 49 of the materials considered have the e(11) coefficient higher than MoS2 insomuch as BrSSb has one of the largest d(11) with a value of 373.0 pm V-1. Moreover, we established a simple empirical model in order to estimate the d(11) coefficients by utilizing the relative ionic motion in the unit cell and the polarizability of the individual elements in the compounds.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000605852800001	Publication Date	2020-12-15
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0953-8984	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	2.649	Times cited		Open Access	Not_Open_Access
	Notes				Approved	Most recent IF: 2.649
	Call Number	UA @ admin @ c:irua:193761			Serial	7971
Permanent link to this record



	Author	Bulut, P.; Beceren, B.; Yildirim, S.; Sevik, C.; Gurel, T.
	Title	Promising room temperature thermoelectric conversion efficiency of zinc-blende AgI from first principles			Type	A1 Journal article
	Year	2021	Publication	Journal Of Physics-Condensed Matter	Abbreviated Journal	J Phys-Condens Mat
	Volume	33	Issue	1	Pages	015501
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	The theoretical investigation on structural, vibrational, and electronic properties of zinc-blende (ZB) AgI were carried out employing first principles density functional theory calculations. Thermoelectric properties then were predicted through semi-classical Boltzmann transport equations within the constant relaxation time approximation. Equilibrium lattice parameter, bulk modulus, elastic constants, and vibrational properties were calculated by using generalized gradient approximation. Calculated properties are in good agreement with available experimental values. Electronic and thermoelectric properties were investigated both with and without considering spin-orbit coupling (SOC) effect which is found to have a strong influence on p-type Seebeck coefficient as well as the power factor of the ZB-AgI. By inclusion of SOC, a reduction of the band-gap and p-type Seebeck coefficients as well as the power factor was found which is the indication of that spin-orbit interaction cannot be ignored for p-type thermoelectric properties of the ZB-AgI. By using deformation potential theory for electronic relaxation time and experimentally predicted lattice thermal conductivity, we obtained aZTvalue 1.69 (0.89) at 400 K for n-type (p-type) carrier concentration of 1.5 x 10(18)(4.6 x10(19)) cm(-3)that makes ZB-AgI as a promising room temperature thermoelectric material.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000577217600001	Publication Date	2020-09-14
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0953-8984	ISBN		Additional Links	UA library record; WoS full record
	Impact Factor	2.649	Times cited		Open Access	Not_Open_Access
	Notes				Approved	Most recent IF: 2.649
	Call Number	UA @ admin @ c:irua:193762			Serial	8425
Permanent link to this record



	Author	Mobaraki, A.; Sevik, C.; Yapicioglu, H.; Cakir, D.; Gulseren, O.
	Title	Temperature-dependent phonon spectrum of transition metal dichalcogenides calculated from the spectral energy density: Lattice thermal conductivity as an application			Type	A1 Journal article
	Year	2019	Publication	Physical review B	Abbreviated Journal
	Volume	100	Issue	3	Pages	035402
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Predicting the mechanical and thermal properties of quasi-two-dimensional (2D) transition metal dichalco-genides (TMDs) is an essential task necessary for their implementation in device applications. Although rigorous density-functional-theory-based calculations are able to predict mechanical and electronic properties, mostly they are limited to zero temperature. Classical molecular dynamics facilitates the investigation of temperature-dependent properties, but its performance highly depends on the potential used for defining interactions between the atoms. In this study, we calculated temperature-dependent phonon properties of single-layer TMDs, namely, MoS2, MoSe2, WS2, and WSe2, by utilizing Stillinger-Weber-type potentials with optimized sets of parameters with respect to the first-principles results. The phonon lifetimes and contribution of each phonon mode in thermal conductivities in these monolayer crystals are systematically investigated by means of the spectralenergy-density method based on molecular dynamics simulations. The obtained results from this approach are in good agreement with previously available results from the Green-Kubo method. Moreover, detailed analysis of lattice thermal conductivity, including temperature-dependent mode decomposition through the entire Brillouin zone, shed more light on the thermal properties of these 2D crystals. The LA and TA acoustic branches contribute most to the lattice thermal conductivity, while ZA mode contribution is less because of the quadratic dispersion around the Brillouin zone center, particularly in MoSe2 due to the phonon anharmonicity, evident from the redshift, especially in optical modes, by increasing temperature. For all the considered 2D crystals, the phonon lifetime values are compelled by transition metal atoms, whereas the group velocity spectrum is dictated by chalcogen atoms. Overall, the lattice thermal conductivity is linearly proportional with inverse temperature.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000473536400003	Publication Date	2019-07-02
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2469-9969; 2469-9950	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor		Times cited		Open Access
	Notes				Approved	no
	Call Number	UA @ admin @ c:irua:193764			Serial	8645
Permanent link to this record



	Author	Kocabas, T.; Ozden, A.; Demiroglu, I.; Cakir, D.; Sevik, C.
	Title	Determination of Dynamically Stable Electrenes toward Ultrafast Charging Battery Applications			Type	A1 Journal article
	Year	2018	Publication	The journal of physical chemistry letters	Abbreviated Journal
	Volume	9	Issue	15	Pages	4267-4274
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	Electrenes, an atomically thin form of layered electrides, are very recent members of the 2D materials family. In this work, we employed first principle calculations to determine stable, exfoliatable, and application-promising 2D electrene materials among possible M2X compounds, where M is a group II-A metal and X is a nonmetal element (C, N, P, As, and Sb). The promise of stable electrene compounds for battery applications is assessed via their exfoliation energy, adsorption properties, and migration energy barriers toward relevant Li, Na, K, and Ca atoms. Our calculations revealed five new stable electrene candidates in addition to previously known Ca2N and Sr2N. Among these seven dynamically stable electrenes, Ba2As, Ba2P, Ba2Sb, Ca2N, Sr2N, and Sr2P are found to be very promising for either K or Na ion batteries due to their extremely low migration energy barriers (5-16 meV), which roughly demonstrates 105 times higher mobility than graphene and two to four times higher mobility than other promising 2D materials such as MXene (Mo2C).
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000440956500020	Publication Date	2018-07-11
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1948-7185	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor		Times cited		Open Access
	Notes				Approved	no
	Call Number	UA @ admin @ c:irua:193765			Serial	7779
Permanent link to this record



	Author	Karaaslan, Y.; Yapicioglu, H.; Sevik, C.
	Title	Assessment of Thermal Transport Properties of Group-III Nitrides: A Classical Molecular Dynamics Study with Transferable Tersoff-Type Interatomic Potentials			Type	A1 Journal article
	Year	2020	Publication	Physical Review Applied	Abbreviated Journal	Phys Rev Appl
	Volume	13	Issue	3	Pages	034027
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	In this study, by means of classical molecular dynamics simulations, we investigate the thermal-transport properties of hexagonal single-layer, zinc-blend, and wurtzite phases of BN, AlN, and GaN crystals, which are very promising for the application and design of high-quality electronic devices. With this in mind, we generate fully transferable Tersoff-type empirical interatomic potential parameter sets by utilizing an optimization procedure based on particle-swarm optimization. The predicted thermal properties as well as the structural, mechanical, and vibrational properties of all materials are in very good agreement with existing experimental and first-principles data. The impact of isotopes on thermal transport is also investigated and between approximately 10 and 50% reduction in phonon thermal transport with random isotope distribution is observed in BN and GaN crystals. Our investigation distinctly shows that the generated parameter sets are fully transferable and very useful in exploring the thermal properties of systems containing these nitrides.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000518820200003	Publication Date	2020-03-10
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2331-7019	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	4.6	Times cited		Open Access
	Notes				Approved	Most recent IF: 4.6; 2020 IF: 4.808
	Call Number	UA @ admin @ c:irua:193766			Serial	7508
Permanent link to this record



	Author	Kandemir, A.; Ozden, A.; Cagin, T.; Sevik, C.
	Title	Thermal conductivity engineering of bulk and one-dimensional Si-Ge nanoarchitectures			Type	A1 Journal article
	Year	2017	Publication	Science and technology of advanced materials	Abbreviated Journal
	Volume	18	Issue	1	Pages	187-196
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Various theoretical and experimental methods are utilized to investigate the thermal conductivity of nanostructured materials; this is a critical parameter to increase performance of thermoelectric devices. Among these methods, equilibrium molecular dynamics (EMD) is an accurate technique to predict lattice thermal conductivity. In this study, by means of systematic EMD simulations, thermal conductivity of bulk Si-Ge structures (pristine, alloy and superlattice) and their nanostructured one dimensional forms with square and circular cross-section geometries (asymmetric and symmetric) are calculated for different crystallographic directions. A comprehensive temperature analysis is evaluated for selected structures as well. The results show that one-dimensional structures are superior candidates in terms of their low lattice thermal conductivity and thermal conductivity tunability by nanostructuring, such as by diameter modulation, interface roughness, periodicity and number of interfaces. We find that thermal conductivity decreases with smaller diameters or cross section areas. Furthermore, interface roughness decreases thermal conductivity with a profound impact. Moreover, we predicted that there is a specific periodicity that gives minimum thermal conductivity in symmetric superlattice structures. The decreasing thermal conductivity is due to the reducing phonon movement in the system due to the effect of the number of interfaces that determine regimes of ballistic and wave transport phenomena. In some nanostructures, such as nanowire superlattices, thermal conductivity of the Si/Ge system can be reduced to nearly twice that of an amorphous silicon thermal conductivity. Additionally, it is found that one crystal orientation, <100>, is better than the <111> crystal orientation in one-dimensional and bulk SiGe systems. Our results clearly point out the importance of lattice thermal conductivity engineering in bulk and nanostructures to produce high-performance thermoelectric materials.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000405949800001	Publication Date	2017-03-13
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1468-6996; 1878-5514	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor		Times cited		Open Access
	Notes				Approved	no
	Call Number	UA @ admin @ c:irua:193772			Serial	8662
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	Author	Ozbal, G.; Senger, R.T.; Sevik, C.; Sevincli, H.
	Title	Ballistic thermoelectric properties of monolayer semiconducting transition metal dichalcogenides and oxides			Type	A1 Journal article
	Year	2019	Publication	Physical review B	Abbreviated Journal
	Volume	100	Issue	8	Pages	085415
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Combining first-principles calculations with Landauer-Mittiker formalism, ballistic thermoelectric transport properties of semiconducting two-dimensional transition metal dichalcogenides (TMDs) and oxides (TMOs) (namely MX2 with M = Cr, Mo, W, Ti, Zr, Hf; X = O, S, Se, Te) are investigated in their 2H and 1T phases. Having computed structural, as well as ballistic electronic and phononic transport properties for all structures, we report the thermoelectric properties of the semiconducting ones. We find that 2H phases of four of the studied structures have very promising thermoelectric properties, unlike their 1T phases. The maximum room temperature p-type thermoelectric figure of merit (ZT) of 1.57 is obtained for 2H-HfSe2, which can be as high as 3.30 at T = 800 K. Additionally, 2H-ZrSe2, 2H-ZrTe2, and 2H-HfS2 have considerable ZT values (both nand p-type), that are above 1 at room temperature. The 1T phases of Zr and Hf-based oxides possess relatively high power factors, however their high lattice thermal conductance values limit their ZT values to below 1 at room temperature.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000480389100007	Publication Date	2019-08-12
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2469-9969; 2469-9950	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor		Times cited		Open Access
	Notes				Approved	no
	Call Number	UA @ admin @ c:irua:193773			Serial	7549
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	Author	Mobaraki, A.; Kandemir, A.; Yapicioglu, H.; Gulseren, O.; Sevik, C.
	Title	Validation of inter-atomic potential for WS2 and WSe2 crystals through assessment of thermal transport properties			Type	A1 Journal article
	Year	2018	Publication	Computational materials science	Abbreviated Journal
	Volume	144	Issue		Pages	92-98
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	In recent years, transition metal dichalcogenides (TMDs) displaying astonishing properties are emerged as a new class of two-dimensional layered materials. The understanding and characterization of thermal transport in these materials are crucial for efficient engineering of 2D TMD materials for applications such as thermoelectric devices or overcoming general overheating issues. In this work, we obtain accurate Stillinger-Weber type empirical potential parameter sets for single-layer WS2 and WSe2 crystals by utilizing particle swarm optimization, a stochastic search algorithm. For both systems, our results are quite consistent with first-principles calculations in terms of bond distances, lattice parameters, elastic constants and vibrational properties. Using the generated potentials, we investigate the effect of temperature on phonon energies and phonon linewidth by employing spectral energy density analysis. We compare the calculated frequency shift with respect to temperature with corresponding experimental data, clearly demonstrating the accuracy of the generated inter-atomic potentials in this study. Also, we evaluate the lattice thermal conductivities of these materials by means of classical molecular dynamics simulations. The predicted thermal properties are in very good agreement with the ones calculated from first-principles. (C) 2017 Elsevier B.V. All rights reserved.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000424902300013	Publication Date	2017-12-16
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0927-0256	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor		Times cited		Open Access
	Notes				Approved	no
	Call Number	UA @ admin @ c:irua:193774			Serial	8729
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	Author	Siriwardane, E.M.D.; Karki, P.; Sevik, C.; Cakir, D.
	Title	Electronic and mechanical properties of stiff rhenium carbide monolayers: A first-principles investigation			Type	A1 Journal article
	Year	2018	Publication	Applied surface science	Abbreviated Journal
	Volume	458	Issue		Pages	762-768
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	In this study, we predicted two new stable metallic Re-C based monolayer structures with a rectangular (r-ReC2) and a hexagonal (h-Re2C) crystal symmetry using first-principle calculations based on density functional theory. Our results obtained from mechanical and phonon calculations and high-temperature molecular dynamic simulations clearly proved the stability of these two-dimensional (2D) crystals. Interestingly, Re-C monolayers in common transition metal carbide structures (i.e. MXenes) were found to be unstable, contrary to expectations. We found that the stable structures, i.e. r-ReC2 and h-Re2C, display superior mechanical properties over the well-known 2D materials. The Young's modulus for r-ReC2 and h-Re2C are extremely high and were calculated as 351 (1310) and 617 (804) N/m (GPa), respectively. Both materials have larger Young's modulus values than the most of the well-known 2D materials. We showed that the combination of the short strong directional p-d bonds, the high coordination number of atoms in the unit-cell and high valence electron density result in strong mechanical properties. Due to its crystal structure, the r-ReC2 monolayer has anisotropic mechanical properties and the crystallographic direction parallel to the C-2 dimers is stiffer compared to perpendicular direction due to strong covalent bonding within C-2 dimers. h-Re2C was derived from the corresponding bulk structure for which we determined the critical thickness for the dynamically stable bulk-derived monolayer structures. In addition, we also investigated the electronic of these two stable structures. Both exhibit metallic behavior and Re-5d orbitals dominate the states around the Fermi level. Due to their ultra high mechanical stability and stiffness, these novel Re-C monolayers can be exploited in various engineering applications.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000441400000088	Publication Date	2018-07-11
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0169-4332	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor		Times cited		Open Access
	Notes				Approved	no
	Call Number	UA @ admin @ c:irua:193776			Serial	7875
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