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	Author	Michel, K.H.; Nikolaev, A.V.
	Title	Theory of distinct crystal structures of polymerized fullerides AC₆₀, A=K, Rb, Cs: the specific role of alkalis			Type	A1 Journal article
	Year	2000	Publication	Physical review letters	Abbreviated Journal	Phys Rev Lett
	Volume	85	Issue		Pages	3197-3200
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	New York, N.Y.	Editor
	Language		Wos	000089807800033	Publication Date	2002-07-27
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0031-9007;1079-7114;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	8.462	Times cited	16	Open Access
	Notes				Approved	Most recent IF: 8.462; 2000 IF: 6.462
	Call Number	UA @ lucian @ c:irua:34339			Serial	3615
Permanent link to this record



	Author	Nikolaev, A.V.; Michel, K.H.
	Title	Electronic structure and electric quadrupoles of a polymerized chain in solid AC₆₀			Type	A1 Journal article
	Year	2001	Publication	Solid state communications	Abbreviated Journal	Solid State Commun
	Volume	117	Issue		Pages	739-743
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	New York, N.Y.	Editor
	Language		Wos	000167538300010	Publication Date	2002-07-25
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0038-1098;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	1.554	Times cited	10	Open Access
	Notes				Approved	Most recent IF: 1.554; 2001 IF: 1.381
	Call Number	UA @ lucian @ c:irua:36881			Serial	1009
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	Author	Nikolaev, A.V.; Michel, K.H.
	Title	Microscopic theory of quadrupolar oredring in TmTe			Type	A1 Journal article
	Year	2001	Publication	Physical review : B : condensed matter and materials physics	Abbreviated Journal	Phys Rev B
	Volume	63	Issue		Pages	1-10
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Lancaster, Pa	Editor
	Language		Wos	000167402100025	Publication Date	2002-07-27
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0163-1829;1095-3795;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.836	Times cited	7	Open Access
	Notes				Approved	Most recent IF: 3.836; 2001 IF: NA
	Call Number	UA @ lucian @ c:irua:36882			Serial	2033
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	Author	Michel, K.H.; Nikolaev, A.V.; Verberck, B.
	Title	Theory of crystal structures of polymerized C₆₀-fullerite and fullerides AC₆₀, A=K, Rb, Cs			Type	H1 Book chapter
	Year	2001	Publication		Abbreviated Journal
	Volume		Issue		Pages
	Keywords	H1 Book chapter; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	s.l.	Editor
	Language		Wos		Publication Date	0000-00-00
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume	462-465	Series Issue		Edition
	ISSN		ISBN		Additional Links	UA library record; WoS full record;
	Impact Factor		Times cited		Open Access
	Notes				Approved	Most recent IF: NA
	Call Number	UA @ lucian @ c:irua:36883			Serial	3614
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	Author	Verberck, B.; Michel, K.H.; Nikolaev, A.V.
	Title	Crystal structures of polymerized fullerides AC₆₀, A=K, Rb, Cs, and alkali-mediated interactions			Type	A1 Journal article
	Year	2002	Publication	The journal of chemical physics	Abbreviated Journal	J Chem Phys
	Volume	116	Issue	23	Pages	10462-10474
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Starting from a model of rigid interacting C-60 polymer chains on an orthorhombic lattice, we study the mutual orientation of the chains and the stability of the crystalline structures Pmnn and I2/m. We take into account (i) van der Waals interactions and electric quadrupole interactions between C-60 monomers on different chains as well as (ii) interactions of the monomers with the surrounding alkali atoms. The direct interactions (i) always lead to an antiferrorotational structure Pmnn with alternate orientation of the C-60 chains in planes (001). The interactions (ii) with the alkalis consist of two parts: translation-rotation (TR) coupling where the orientations of the chains interact with displacements of the alkalis, and quadrupolar electronic polarizability (ep) coupling, where the electric quadrupoles on the C-60 monomers interact with induced quadrupoles due to excited electronic d-states of the alkalis. Both interactions (ii) lead to an effective orientation-orientation interaction between the C-60 chains and always favor the ferrorotational structure I2/m, where C-60 chains have a same orientation. The structures Pmnn for KC60 and I2/m for Rb- and CsC60 are the result of a competition between the direct interaction (i) and the alkali-mediated interactions (ii). In Rb- and CsC60 the latter are found to be dominant, the preponderant role being played by the quadrupolar electronic polarizability of the alkali ions. (C) 2002 American Institute of Physics.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	New York, N.Y.	Editor
	Language		Wos	000175905800044	Publication Date	2002-07-26
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0021-9606;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	2.965	Times cited	12	Open Access
	Notes				Approved	Most recent IF: 2.965; 2002 IF: 2.998
	Call Number	UA @ lucian @ c:irua:103350			Serial	578
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	Author	Nikolaev, A.V.; Michel, K.H.
	Title	Molecular terms and optical transitions of C₆₀^n+/- molecular ions			Type	P1 Proceeding
	Year	2002	Publication	AIP conference proceedings T2 – 16th International Winterschool on Electronic Properties of Novel, Materials, MAR 02-09, 2002, KIRCHBERG, AUSTRIA	Abbreviated Journal
	Volume		Issue		Pages	417-420
	Keywords	P1 Proceeding; Condensed Matter Theory (CMT)
	Abstract	We have studied the molecular energy terms of the hole configurations (h(u)(+))(m), m=2,3,4,5 of C-60(m+) cations and the electronic configurations (t(1u))(n) n=2,3,4, as well as (t(1u))(n-1)t(1g) of the C-60(n-) anions. The lowest terms (within an energy span of 0.03 eV) for C-60(2+) are three triplets T-3(1g), (3)G(g), T-3(2g) and for C-60(3+) are three quartets T-4(1u), (4)G(u), T-4(2u), which favor Jahn-Teller distortions. For the ground state of C-60(2-) we find a triplet T-3(1g) in agreement with Hund's rules. Our method takes into account intramolecular direct and exchange multipolar Coulomb interactions.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	New York	Editor
	Language		Wos		Publication Date	0000-00-00
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume	633	Series Issue		Edition
	ISSN	0-7354-0088-1	ISBN		Additional Links	UA library record; WoS full record;
	Impact Factor		Times cited		Open Access
	Notes				Approved	Most recent IF: NA
	Call Number	UA @ lucian @ c:irua:103905			Serial	2187
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	Author	Verberck, B.; Nikolaev, A.V.; Michel, K.H.
	Title	Theoretical model for the structural phase transition at the metal-insulator transition in polymerized KC₆₀			Type	A1 Journal article
	Year	2002	Publication	Physical Review B	Abbreviated Journal	Phys Rev B
	Volume	66	Issue	16	Pages	165425-165425,14
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	The recently discovered structural transition in polymerized KC60 at about 50 K results in a doubling of the unit cell volume and accompanies the metal-insulator transition. Here we show that the ((a) over right arrow+(c) over right arrow,(b) over right arrow,(a) over right arrow-(c) over right arrow) superstructure results from small orientational charge density waves along the polymer chains and concomitant displacements of the surrounding K+ ions. The effect is specific for the space group Pmnn of KC60 and is absent in RbC60 and CsC60 (space group I2/m). The mechanism is relevant for the metal-insulator transition.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000179286400135	Publication Date	2002-10-30
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0163-1829;1095-3795;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.836	Times cited	10	Open Access
	Notes				Approved	Most recent IF: 3.836; 2002 IF: NA
	Call Number	UA @ lucian @ c:irua:94907			Serial	3608
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	Author	Nikolaev, A.V.; Michel, K.H.
	Title	Many electron- and hole terms of molecular ions C₆₀^n\pm			Type	A1 Journal article
	Year	2003	Publication	Coupling In Chemistry And Physics	Abbreviated Journal	Adv Quantum Chem
	Volume	44	Issue		Pages	305-312
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	New York, N.Y.	Editor
	Language		Wos	000188940800019	Publication Date	2004-05-19
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0065-3276;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	1.196	Times cited	1	Open Access
	Notes				Approved	Most recent IF: 1.196; 2003 IF: 0.375
	Call Number	UA @ lucian @ c:irua:104131			Serial	1942
Permanent link to this record



	Author	Nikolaev, A.V.; Michel, K.H.
	Title	Symmetry lowering at the structural phase transitions in NpO₂ and UO₂			Type	A1 Journal article
	Year	2003	Publication	Physical review : B : condensed matter and materials physics	Abbreviated Journal	Phys Rev B
	Volume	68	Issue	5	Pages	054112-054112,7
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	The structural phase transitions with electric-quadrupole long-range order in NpO2 (Fm (3) over barm-->Pn (3) over barm) and UO2 (Fm (3) over barm-->Pa (3) over bar) are analyzed from a group theoretical point of view. In both cases, the symmetry lowering involves three quadrupolar components belonging to the irreducible representation T-2g (Gamma(5)) of O-h and condensing in a triple-q structure at the X point of the Brillouin zone. The Pa (3) over bar structure is close to Pn (3) over barm, but allows for oxygen displacements. The Pa (3) over bar ordering leads to an effective electrostatic attraction between electronic quadrupoles while the Pn (3) over barm ordering results in a repulsion between them. It is concluded that the Pn (3) over barm structure can be stabilized only through some additional process such as strengthening of the chemical bonding between Np and O. We also derive the relevant structure-factor amplitudes for Pn (3) over barm and Pa (3) over bar, and the effect of domains on resonant x-ray scattering experiments.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000185240100038	Publication Date	2003-08-29
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0163-1829;1095-3795;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.836	Times cited	15	Open Access
	Notes				Approved	Most recent IF: 3.836; 2003 IF: NA
	Call Number	UA @ lucian @ c:irua:94847			Serial	3405
Permanent link to this record



	Author	Nikolaev, A.V.; Michel, K.H.
	Title	Ab initio approach to superexchange interactions in alkali doped fullerides AC₆₀			Type	P1 Proceeding
	Year	2004	Publication	AIP conference proceedings T2 – 18th International Winterschool/Euroconference on Electronic Properties, of Novel Materials, MAR 06-JUN 13, 2004, Kirchberg, AUSTRIA	Abbreviated Journal
	Volume		Issue		Pages	393-396
	Keywords	P1 Proceeding; Condensed Matter Theory (CMT)
	Abstract	The superexchange interactions between the fullerenes arise as a result of the electron transfer from the C-60 molecule to the alkali atom and back. We present a scheme, which is a configuration interaction approach based on the valence bond (Heitler-London) method. The effect of superexchange is described together with chemical bonding by constructing and solving a secular equation, rather than by using a perturbation treatment. We have considered 180degrees and 90degrees superexchange for the C-60 Cs-C-60 pathways. The calculations account for unusual electronic properties of polymer orthorhombic and quenched cubic phases of CsC60: two lines in nuclear magnetic resonance experiments, the development of a spin-singlet ground state and a decrease of magnetic susceptibility as T-->0.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	New York	Editor
	Language		Wos	000224699400085	Publication Date	2004-11-11
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume	723	Series Issue		Edition
	ISSN	0-7354-0204-3	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor		Times cited		Open Access
	Notes				Approved	Most recent IF: NA
	Call Number	UA @ lucian @ c:irua:103752			Serial	27
Permanent link to this record



	Author	Mattauch, S.; Heger, G.; Michel, K.H.
	Title	High resolution neutron and X-ray diffraction studies as a function of temperature and electric field of the ferroelectric phase transition of RDP			Type	A1 Journal article
	Year	2004	Publication	Crystal research and technology	Abbreviated Journal	Cryst Res Technol
	Volume	39	Issue	12	Pages	1027-1054
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Neutron and high resolution X-ray diffraction investigations on perfect single crystals of RbH2PO4 (RDP), a hydrogen bonded ferroelectric of KDP type are reported. The results of crystal structure analysis from diffraction data, below and above the paraelectric – ferroelectric phase transition, support a disorder – order character Of [PO4H2](-)-groups. The tetragonal symmetry of the paraelectric phase with the double well potential of the hydrogen atoms obtained by diffraction, results simply from a time-space average of orthorhombic symmetry. According to the group – subgroup relation between the tetragonal space group 142d and the orthorhombic Fdd2 a short range order of ferroelectric clusters in the tetragonal phase is observed. With decreasing temperature the ferroelectric clusters increase and the long range interaction between their local polarisation vectors leads to the formation of lamellar ferroelectric domains with alternating polarisation directions at T-C = 147 K. From the high resolution X-ray data it is concluded that below T-C the ferroelastic strain in the (a,b)-plane leads to micro-angle grain boundaries at the domain walls. The tilt angle is enhanced by an applied electric field parallel to the ferroelectric axis. The resulting dislocations at the domain walls persist in the paraelectric phase leading to a memory effect for the arrangement of twin lamellae. With increased electric field the phase transition temperature T-C is decreased.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Berlin	Editor
	Language		Wos	000225681100001	Publication Date	2004-11-12
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0232-1300;1521-4079;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	1	Times cited	12	Open Access
	Notes				Approved	Most recent IF: 1; 2004 IF: 0.770
	Call Number	UA @ lucian @ c:irua:94785			Serial	1459
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	Author	Verberck, B.; Nikolaev, A.V.; Michel, K.H.
	Title	Orientational charge density waves and the metal-insulator transition in polymerized KC60			Type	A1 Journal article
	Year	2004	Publication	AIP conference proceedings	Abbreviated Journal
	Volume	723	Issue		Pages	339-342
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Polymerized KC60 undergoes a structural phase transition accompanied by a metal-insulator transition around 50 K. To explain the structural aspect, a mechanism involving small orientational deviations of the valence electron density on every C-60 monomer orientational charge density waves (OCDWs) – has already been proposed earlier. In the present work, we address the metal-insulator transition using the OCDW concept. We are inspired by the analogy between a polymer chain exhibiting an OCDW and a linear atomic chain undergoing a static lattice deformation doubling the unit cell: such a deformation implies a band gap at the zone boundary, yielding an insulating state (Peierls instability). Within our view, a similar mechanism occurs in polymerized KC60; the OCDW plays the role of the lattice deformation. We present tight-binding band structure calculations and conclude that the metal-insulator transition can indeed be explained using OCDWs, but that the threedimensionality of the crystal plays an unexpected key role.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	New York	Editor
	Language		Wos		Publication Date	0000-00-00
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0094-243x	ISBN		Additional Links	UA library record; WoS full record;
	Impact Factor		Times cited		Open Access
	Notes				Approved	Most recent IF: NA
	Call Number	UA @ lucian @ c:irua:94831			Serial	2513
Permanent link to this record



	Author	Verberck, B.; Nikolaev, A.V.; Michel, K.H.
	Title	Theoretical model for the structural phase transition and the metal-insulator transition in polymerized KC₆₀			Type	A1 Journal article
	Year	2004	Publication	Fullerenes, nanotubes, and carbon nanostructures T2 – 6th Biennial International Workshop on Fullerenes and Atomic Clusters, JUN 30-JUL 04, 2003, St Petersburg, RUSSIA	Abbreviated Journal	Fuller Nanotub Car N
	Volume	12	Issue	1-2	Pages	243-252
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	The recently discovered structural phase transition in Polymerized KC60 at about 50K leads to a doubling of the unit cell volume and is accompanied by a metal-insulator transition. Here, we show that the ((a) over right arrow + (c) over right arrow, (b) over right arrow, (a) over right arrow – (c) over right arrow) superstructure results from orientational charge density waves along the polymer chains and correlated displacements of the K+ ions. The presented model can also account for the metal-insulator transition. The effect is specific for the space group Pmnn of KC60 and is absent in both Rb- and CsC60 (space group 12/m), in agreement with the present experimental knowledge of these compounds.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000220551600040	Publication Date	2004-03-15
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1536-383X;1536-4046;	ISBN		Additional Links	UA library record; WoS full record
	Impact Factor	1.35	Times cited		Open Access
	Notes				Approved	Most recent IF: 1.35; 2004 IF: 1.117
	Call Number	UA @ lucian @ c:irua:103259			Serial	3607
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	Author	Michel, K.H.; Verberck, B.; Nikolaev, A.V.
	Title	Anisotropic packing and one-dimensional fluctuations of C₆₀ molecules in carbon nanotubes			Type	A1 Journal article
	Year	2005	Publication	Physical review letters	Abbreviated Journal	Phys Rev Lett
	Volume	95	Issue	18	Pages	185506-185506,4
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	The confinement of a C-60 molecule encapsulated in a cylindrical nanotube depends on the tube radius. In small tubes with radius R-T less than or similar to 7 A, a fivefold axis of the molecule coincides with the tube axis. The interaction between C-60 molecules in the nanotube is then described by a O-2-rotor model on a 1D liquid chain with coupling between orientational and displacive correlations. This coupling leads to chain contraction. The structure factor of the 1D liquid is derived. In tubes with a larger radius the molecular centers of mass are displaced off the tube axis. The distinction of two groups of peapods with on- and off-axis molecules suggests an explanation of the apparent splitting of A(g) modes of C-60 in nanotubes measured by resonant Raman scattering.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	New York, N.Y.	Editor
	Language		Wos	000232887400041	Publication Date	2005-10-28
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0031-9007;1079-7114;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	8.462	Times cited	40	Open Access
	Notes				Approved	Most recent IF: 8.462; 2005 IF: 7.489
	Call Number	UA @ lucian @ c:irua:94717			Serial	127
Permanent link to this record



	Author	Michel, K.H.; Verberck, B.; Nikolaev, A.
	Title	Mercator maps of orientations of a C₆₀ molecule in single-walled nanotubes with distinct radii			Type	A1 Journal article
	Year	2005	Publication	AIP conference proceedings	Abbreviated Journal
	Volume	786	Issue		Pages	69-72
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	We study the confinement of a C-60 molecule encapsulated in a cylindrical nanotube as a function of the tube radius. Drawing the Mercator maps of the potential, we find two distinct molecular orientations; for tubes with small radii, R-T less than or similar to 7 angstrom, a fivefold axis of the molecule coincides with the tube long axis, for larger radii, R-T less than or similar to 8 angstrom, a threefold axis of the molecule coincides with the tube long axis. These different orientations are caused by the relative importance of the repulsive and the attractive parts of the van der Waals potentials of the molecule with the tube wall for small and large tubes respectively. Experimental evidence is provided by the apparent splitting of A(g) modes of the C-60 molecule in resonant Raman scattering.
	Address
	Corporate Author				Thesis
	Publisher	Amer inst physics	Place of Publication	Melville	Editor
	Language		Wos		Publication Date	0000-00-00
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0094-243x	ISBN		Additional Links	UA library record; WoS full record;
	Impact Factor		Times cited		Open Access
	Notes				Approved	Most recent IF: NA
	Call Number	UA @ lucian @ c:irua:94738			Serial	1993
Permanent link to this record



	Author	Michel, K.H.; Verberck, B.; Nikolaev, A.V.
	Title	Nanotube field and one-dimensional fluctuations of C₆₀ molecules in carbon nanotubes			Type	A1 Journal article
	Year	2005	Publication	European physical journal : B : condensed matter and complex systems	Abbreviated Journal	Eur Phys J B
	Volume	48	Issue	1	Pages	113-124
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Berlin	Editor
	Language		Wos	000233998600016	Publication Date	2005-12-13
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1434-6028;1434-6036;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	1.461	Times cited	25	Open Access
	Notes				Approved	Most recent IF: 1.461; 2005 IF: 1.720
	Call Number	UA @ lucian @ c:irua:56408			Serial	2279
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	Author	Verberck, B.; Nikolaev, A.V.; Michel, K.H.
	Title	Orientational charge density waves and the metal-insulator transition in polymerized KC₆₀			Type	A1 Journal article
	Year	2005	Publication	Physical review : B : condensed matter and materials physics	Abbreviated Journal	Phys Rev B
	Volume	71	Issue	16	Pages	165117-11
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	A theoretical model is presented for the description of the metal-insulator transition which accompanies the structural phase transition at T approximate to 50 K in polymerized KC60. The model involves orientational charge density waves (along the C-60 polymer chains) which were introduced previously for a description of the structural phase transition. A satisfactory qualitative and quantitative understanding is obtained when the three-dimensionality of the crystal and the presence of the K+ counterions is properly taken into account.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000228763100035	Publication Date	2005-04-27
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1098-0121;1550-235X;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.836	Times cited	1	Open Access
	Notes				Approved	Most recent IF: 3.836; 2005 IF: 3.185
	Call Number	UA @ lucian @ c:irua:104076			Serial	2514
Permanent link to this record



	Author	Nikolaev, A.V.; Michel, K.H.
	Title	Superexchange and electron correlations in alkali fullerides AC₆₀, A=K, Rb, Cs			Type	A1 Journal article
	Year	2005	Publication	The journal of chemical physics	Abbreviated Journal	J Chem Phys
	Volume	122	Issue	6	Pages	064310-64314
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Superexchange interactions in alkali fullerides AC(60) are derived for C-60 molecular ions separated by interstitial alkali-metal ions. We use a multiconfiguration approach which comprises the lowest molecular orbital states of the C-60 molecule and the excited s and d states of the alkali-metal atom A. Interactions are described by the valence bond (Heitler-London) method for a complex (C-60 – A – C-60) – with two valence electrons. The electronic charge transfer between the alkali-metal atom and a neighboring C-60 molecule is not complete. The occupation probability of excited d and s states of the alkali atom is not negligible. In correspondence with the relative positions of the C-60 molecules and A atoms in the polymer crystal, we consider 180degrees and 90degrees (angle) superexchange pathways. For the former case the ground state is found to be a spin singlet separated from a triplet at similar to20 K. For T < 20 K there appear strong spin correlations for the 180degrees superexchange pathway. The results are related to spin lattice relaxation experiments on CsC60 in the polymerized and in the quenched cubic phase. (C) 2005 American Institute of Physics.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	New York, N.Y.	Editor
	Language		Wos	000226918100018	Publication Date	2005-02-02
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0021-9606;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	2.965	Times cited	11	Open Access
	Notes				Approved	Most recent IF: 2.965; 2005 IF: 3.138
	Call Number	UA @ lucian @ c:irua:102740			Serial	3377
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	Author	Verberck, B.; Michel, K.H.
	Title	Nanotube field of C₆₀ molecules in carbon nanotubes: atomistic versus continuous approach			Type	A1 Journal article
	Year	2006	Publication	Physical review : B : condensed matter and materials physics	Abbreviated Journal	Phys Rev B
	Volume	74	Issue	4	Pages	045421,1-14
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Lancaster, Pa	Editor
	Language		Wos	000239426800113	Publication Date	2006-07-22
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1098-0121;1550-235X;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.836	Times cited	31	Open Access
	Notes				Approved	Most recent IF: 3.836; 2006 IF: 3.107
	Call Number	UA @ lucian @ c:irua:60090			Serial	2281
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	Author	Verberck, B.; Michel, K.H.; Nikolaev, A.V.
	Title	The C₆₀ molecules in (C₆₀)_N@SWCNT peapods: crystal field, intermolecular interactions and dynamics			Type	A1 Journal article
	Year	2006	Publication	Fullerenes, nanotubes, and carbon nanostructures	Abbreviated Journal	Fuller Nanotub Car N
	Volume	14	Issue	2/3	Pages	171-178
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000238762900006	Publication Date	2006-06-08
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1536-383X;1536-4046;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	1.35	Times cited	10	Open Access
	Notes				Approved	Most recent IF: 1.35; 2006 IF: 0.462
	Call Number	UA @ lucian @ c:irua:60025			Serial	3518
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	Author	Verberck, B.; Michel, K.H.
	Title	Anisotropic packing of C-70 molecules in carbon nanotubes			Type	A1 Journal article
	Year	2007	Publication	Physica status solidi B-basic solid state physics	Abbreviated Journal	Phys Status Solidi B
	Volume	244	Issue	11	Pages	4279-4282
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000251355800092	Publication Date	2007-10-19
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0370-1972;1521-3951;	ISBN		Additional Links	UA library record; WoS full record
	Impact Factor	1.674	Times cited		Open Access
	Notes				Approved	Most recent IF: 1.674; 2007 IF: 1.071
	Call Number	UA @ lucian @ c:irua:67350			Serial	128
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	Author	Verberck, B.; Michel, K.H.
	Title	Nanotube field and orientational properties of C₇₀ molecules in carbon nanotubes			Type	A1 Journal article
	Year	2007	Publication	Physical review : B : condensed matter and materials physics	Abbreviated Journal	Phys Rev B
	Volume	75	Issue	4	Pages	045419,1-14
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	The orientation of a C(70) fullerene molecule encapsulated in a single-walled carbon nanotube (SWCNT) depends on the tube radius. First we confirm that chirality effects do not affect the orientation as well by comparing discrete atomistic calculations with the results of a continuous tube approximation for a variety of SWCNTs. The molecular and the tube symmetry are exploited by using symmetry-adapted rotator functions. We accurately determine the optimal molecular orientation as a function of the tube radius; for low (less than or similar to 7 A) and high (greater than or similar to 7.2 A) tube radii, lying and standing molecular orientations are recovered, respectively. In between, we observe a transition regime. In addition, we consider off-axis positions. We perform a one-dimensional liquid description of a chain of on-axis C(70) molecules inside a SWCNT. All results agree well with recent x-ray diffraction experiments.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Lancaster, Pa	Editor
	Language		Wos	000243895600128	Publication Date	2007-01-17
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1098-0121;1550-235X;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.836	Times cited	23	Open Access
	Notes				Approved	Most recent IF: 3.836; 2007 IF: 3.172
	Call Number	UA @ lucian @ c:irua:63752			Serial	2280
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	Author	Verberck, B.; Michel, K.H.
	Title	Nanotube field of C₆₀ and C₇₀ molecules in carbon nanotubes			Type	A1 Journal article
	Year	2007	Publication	International journal of quantum chemistry	Abbreviated Journal	Int J Quantum Chem
	Volume	107	Issue	13	Pages	2294-2319
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	New York, N.Y.	Editor
	Language		Wos	000249459800002	Publication Date	2007-02-20
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0020-7608;1097-461X;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	2.92	Times cited	6	Open Access
	Notes				Approved	Most recent IF: 2.92; 2007 IF: 1.368
	Call Number	UA @ lucian @ c:irua:65785			Serial	2282
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	Author	Michel, K.H.; Verberck, B.; Hulman, M.; Kuzmany, H.; Krause, M.
	Title	Superposition of quantum and classical rotational motions in Sc₂C₂@C₈₄ fullerite			Type	A1 Journal article
	Year	2007	Publication	The journal of chemical physics	Abbreviated Journal	J Chem Phys
	Volume	126	Issue	6	Pages	064304,1-15
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	New York, N.Y.	Editor
	Language		Wos	000244250200008	Publication Date	2007-02-09
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0021-9606;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	2.965	Times cited	14	Open Access
	Notes				Approved	Most recent IF: 2.965; 2007 IF: 3.044
	Call Number	UA @ lucian @ c:irua:63628			Serial	3381
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	Author	Verberck, B.; Heresanu, V.; Rouziere, S.; Cambedouzou, J.; Launois, P.; Kovats, E.; Pekker, S.; Vliegenthart, G.A.; Michel, K.H.; Gompper, G.
	Title	Fullerene-cubane : X-ray scattering experiments and Monte Carlo simulations			Type	A1 Journal article
	Year	2008	Publication	Fullerenes, nanotubes, and carbon nanostructures T2 – 8th Biennial International Workshop on Fullerenes and Atomic Clusters, (IWFAC 2007), JUL 02-06, 2007, St Petersburg, RUSSIA	Abbreviated Journal	Fuller Nanotub Car N
	Volume	16	Issue	5-6	Pages	293-300
	Keywords	A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
	Abstract	We report single-crystal X-ray diffuse scattering measurements on C-60.C8H8 fullerene-cubane showing that the C-60 molecules are orientationally disordered at 300 and 150K and get ordered at low temperatures. Monte Carlo simulations provide further insight in the orientational behavior of both C-60 and C8H8 molecules; low-temperature molecular orientations are predicted.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000259645200003	Publication Date	2008-09-28
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1536-383X;1536-4046;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	1.35	Times cited	6	Open Access
	Notes				Approved	Most recent IF: 1.35; 2008 IF: 0.680
	Call Number	UA @ lucian @ c:irua:102640			Serial	1295
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	Author	Michel, K.H.; Verberck, B.
	Title	Theory of the elastic constants of graphite and graphene			Type	A1 Journal article
	Year	2008	Publication	Physica status solidi: B: basic research	Abbreviated Journal	Phys Status Solidi B
	Volume	245	Issue	10	Pages	2177-2180
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Born's long wave method is used to study the elastic properties of graphite and graphene. Starting from an empirical force constant model derived from full inplane phonon dispersions of graphite [Mohr et al., Phys. Rev. B 76, 035439 (2007)] we calculate the tension coefficients of graphene. Extending the model by interplanar interactions, we calculate the elastic constants of graphite. The agreement of our theoretical values with inelastic x-ray scattering results on elastic constants of graphite [Bosak et al., Phys. Rev. B 75, 153408 (2007)] is very satisfactory.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Berlin	Editor
	Language		Wos	000260581800066	Publication Date	2008-08-25
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0370-1972;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	1.674	Times cited	47	Open Access
	Notes				Approved	Most recent IF: 1.674; 2008 IF: 1.166
	Call Number	UA @ lucian @ c:irua:75660			Serial	3621
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	Author	Michel, K.H.; Verberck, B.
	Title	Theory of the evolution of phonon spectra and elastic constants from graphene to graphite			Type	A1 Journal article
	Year	2008	Publication	Physical review : B : solid state	Abbreviated Journal	Phys Rev B
	Volume	78	Issue	8	Pages	085424,1-085424,17
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	We present a unified theory of the phonon dispersions and elastic properties of graphene, graphite, and graphene multilayer systems. Starting from a fifth-nearest-neighbor force-constant model derived from full in-plane phonon dispersions of graphite [Mohr et al., Phys. Rev. B 76, 035439 (2007)], we use Born's long-wave method to calculate the tension and bending coefficients of graphene. Extending the model by interplanar interactions, we study the phonon dispersions and the elastic constants of graphite, and the phonon spectra of graphene multilayers. We find that the inner displacement terms due to sublattice shifts between inequivalent C atoms are quantitatively important in determining the elastomechanical properties of graphene and of graphite. The overall agreement between theory and experiment is very satisfactory. We investigate the evolution from graphene to graphite by studying the increase in the rigid plane optical mode as a function of the number of layers N. At N=10 the graphite value B2g1127 cm−1 is attained within a few percent.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Lancaster, Pa	Editor
	Language		Wos	000259406900106	Publication Date	2008-08-21
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1098-0121;1550-235X;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.836	Times cited	72	Open Access
	Notes				Approved	Most recent IF: 3.836; 2008 IF: 3.322
	Call Number	UA @ lucian @ c:irua:76527			Serial	3622
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	Author	Nikolaev, A.V.; Michel, K.H.
	Title	Elusive s-f intrasite interactions and double exchange in solids: ferromagnetic versus nonmagnetic ground state			Type	A1 Journal article
	Year	2009	Publication	Journal of experimental and theoretical physics	Abbreviated Journal	J Exp Theor Phys+
	Volume	109	Issue	2	Pages	286-292
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	From the theory of many-electron states in atoms, we know that there exists a strong Coulomb repulsion, which results in the electronic term structure of atoms and is responsible for Hunds rules. By expanding the Coulomb on-site repulsion into a multipolar series, we derive this interaction and show that it is also present in solids as a correlation effect, which means that the interaction requires a multideterminant version of the Hartree-Fock method. Of particular interest is the case where this interaction couples states of localized ( f) and delocalized ( s) electrons. We show that the interaction is bilinear in the creation/annihilation operators for localized electrons and bilinear in the operators for conduction electrons. To study the coupling, we consider a simple model in the framework of an effective limited configuration interaction method with one localized f-electron and one itinerant s-electron per crystal site. The on-site multipole interaction between the f- and s-electrons is explicitly taken into account. It is shown that depending on the low-lying excitation spectrum imposed by the crystal electric field, the model can lead not only to ferromagnetism but also to a nonmagnetic state. The model is relevant for solids with localized and itinerant electron states.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Woodbury, N.Y.	Editor
	Language		Wos	000270506500014	Publication Date	2009-09-18
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1063-7761;1090-6509;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	1.196	Times cited	3	Open Access
	Notes				Approved	Most recent IF: 1.196; 2009 IF: 0.871
	Call Number	UA @ lucian @ c:irua:79163			Serial	1027
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	Author	Michel, K.H.; Verberck, B.
	Title	Theoretical phonon dispersions in monolayers and multilayers of hexagonal boron-nitride			Type	A1 Journal article
	Year	2009	Publication	Physica status solidi: B: basic research	Abbreviated Journal	Phys Status Solidi B
	Volume	246	Issue	11/12	Pages	2802-2805
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Starting from an empirical force constant model of valence interactions and calculating by Ewald's method the electrostatic force constants, we derive the dynamical matrix for a monolayer and for multilayer systems of hexagonal boron nitride (h-BN). Solution of the secular problem leads to the corresponding phonon dispersion relations. The interplay between valence forces and Coulomb forces is discussed. A comparison with previous results on graphene and graphene multilayers is made. Our spectra on the h-BN monolayer are rather similar to previous ab initio theory results. Comparison is also made with Raman and infrared experimental results.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Berlin	Editor
	Language		Wos	000272904100091	Publication Date	2009-11-12
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0370-1972;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	1.674	Times cited	10	Open Access
	Notes				Approved	Most recent IF: 1.674; 2009 IF: 1.150
	Call Number	UA @ lucian @ c:irua:80673			Serial	3609
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	Author	Michel, K.H.; Verberck, B.
	Title	Theory of elastic and piezoelectric effects in two-dimensional hexagonal boron nitride			Type	A1 Journal article
	Year	2009	Publication	Physical review : B : solid state	Abbreviated Journal	Phys Rev B
	Volume	80	Issue	22	Pages	224301,1-224301,10
	Keywords	A1 Journal article; Condensed Matter Theory (CMT)
	Abstract	Starting from an empirical force constant model of valence interactions and calculating by Ewalds method the ion-ion force constants, we derive the dynamical matrix for a monolayer crystal of hexagonal boron nitride (h-BN). The phonon dispersion relations are calculated. The interplay between valence and Coulomb forces is discussed. It is shown by analytical methods that the longitudinal and the transverse optical (LO and TO) phonon branches for in-plane motion are degenerate at the Γ point of the Brillouin zone. Away from Γ, the LO branch exhibits pronounced overbending. It is found that the nonanalytic Coulomb contribution to the dynamical matrix causes a linear increase of the LO branch with increasing wave vector starting at Γ. This effect is general for two-dimensional (2D) ionic crystals. Performing a long-wavelength expansion of the dynamical matrix, we use Borns perturbation method to calculate the elastic constants (tension coefficients). Since the crystal is noncentrosymmetric, internal displacements due to relative shifts between the two sublattices (B and N) contribute to the elastic constants. These internal displacements are responsible for piezoelectric and dielectric phenomena. The piezoelectric stress constant and the dielectric susceptibility of 2D h-BN are calculated.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Lancaster, Pa	Editor
	Language		Wos	000273228500045	Publication Date	2009-12-21
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1098-0121;1550-235X;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	3.836	Times cited	96	Open Access
	Notes				Approved	Most recent IF: 3.836; 2009 IF: 3.475
	Call Number	UA @ lucian @ c:irua:80576			Serial	3616
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