| |
Records |
Links |
|
Author |
Michel, K.H.; Verberck, B. |
|
| |
Title |
Theory of rigid-plane phonon modes in layered crystals |
Type |
A1 Journal article |
| |
Year |
2012 |
Publication  |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
|
| |
Volume |
85 |
Issue |
9 |
Pages |
094303-094303,11 |
|
| |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
|
| |
Abstract |
The lattice dynamics of low-frequency rigid-plane modes in metallic (graphene multilayers, GML) and in insulating (hexagonal boron-nitride multilayers, BNML) layered crystals is investigated. The frequencies of shearing and compression (stretching) modes depend on the layer number N and are presented in the form of fan diagrams. The results for GML and BNML are very similar. In both cases, only the interactions (van der Waals and Coulomb) between nearest-neighbor planes are effective, while the interactions between more distant planes are screened. A comparison with recent Raman scattering results on low-frequency shear modes in GML [Tan et al., Nat. Mater., in press, doi: 10.1038/nmat3245, (2012)] is made. Relations with the low-lying rigid-plane phonon dispersions in the bulk materials are established. Master curves, which connect the fan diagram frequencies for any given N, are derived. Static and dynamic thermal correlation functions for rigid-layer shear and compression modes are calculated. The results might be of use for the interpretation of friction force experiments on multilayer crystals. |
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Wos |
000301646000006 |
Publication Date |
2012-03-19 |
|
| |
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 |
38 |
Open Access |
|
|
| |
Notes |
; The authors are indebted to J. Maultzsch for bringing Ref. 20 to their attention. They thank D. Lamoen, F.M. Peeters, B. Trauzettel, and C. Van Haesendonck for useful discussions. This work has been financially supported by the Research Foundation Flanders (FWO). ; |
Approved |
Most recent IF: 3.836; 2012 IF: 3.767 |
|
| |
Call Number |
UA @ lucian @ c:irua:97787 |
Serial |
3619 |
|
| Permanent link to this record |
| |
|
| |
|
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 |
|
| Permanent link to this record |
| |
|
| |
|
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 |
|
| Permanent link to this record |
| |
|
| |
|
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 |
|
| Permanent link to this record |
| |
|
| |
|
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 |
Varykhalov, A.; Marchenko, D.; Sanchez-Barriga, J.; Scholz, M.R.; Verberck, B.; Trauzettel, B.; Wehling, T.O.; Carbone, C.; Rader, O. |
|
| |
Title |
Intact dirac cones at broken sublattice symmetry : photoemission study of graphene on Ni and Co |
Type |
A1 Journal article |
| |
Year |
2012 |
Publication |
Physical review X |
Abbreviated Journal |
Phys Rev X |
|
| |
Volume |
2 |
Issue |
4 |
Pages |
041017-10 |
|
| |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
|
| |
Abstract |
The appearance of massless Dirac fermions in graphene requires two equivalent carbon sublattices of trigonal shape. While the generation of an effective mass and a band gap at the Dirac point remains an unresolved problem for freestanding extended graphene, it is well established by breaking translational symmetry by confinement and by breaking sublattice symmetry by interaction with a substrate. One of the strongest sublattice-symmetry-breaking interactions with predicted and measured band gaps ranging from 400 meV to more than 3 eV has been attributed to the interfaces of graphene with Ni and Co, which are also promising spin-filter interfaces. Here, we apply angle-resolved photoemission to epitaxial graphene on Ni (111) and Co(0001) to show the presence of intact Dirac cones 2.8 eV below the Fermi level. Our results challenge the common belief that the breaking of sublattice symmetry by a substrate and the opening of the band gap at the Dirac energy are in a straightforward relation. A simple effective model of a biased bilayer structure composed of graphene and a sublattice-symmetry-broken layer, corroborated by density-functional-theory calculations, demonstrates the general validity of our conclusions. |
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
College Park, Md |
Editor |
|
|
| |
Language |
|
Wos |
000312703200001 |
Publication Date |
2012-12-22 |
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
2160-3308; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
|
| |
Impact Factor |
12.789 |
Times cited |
86 |
Open Access |
|
|
| |
Notes |
; A. V. acknowledges helpful discussions with N. Sandler. This work was supported by SPP 1459 of the Deutsche Forschungsgemeinschaft. B. V. acknowledges support from the Research Foundation Flanders (FWO-Vlaanderen). B. T. and T. O. W. would like to thank the KITP at Santa Barbara for hospitality during the completion of this work. ; |
Approved |
Most recent IF: 12.789; 2012 IF: 6.711 |
|
| |
Call Number |
UA @ lucian @ c:irua:105964 |
Serial |
1677 |
|
| Permanent link to this record |
| |
|
| |
|
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 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Verberck, B.; Vliegenthart, G.A.; Gompper, G. |
|
| |
Title |
Orientational ordering in solid C60 fullerene-cubane |
Type |
A1 Journal article |
| |
Year |
2009 |
Publication |
The journal of chemical physics |
Abbreviated Journal |
J Chem Phys |
|
| |
Volume |
130 |
Issue |
15 |
Pages |
154510,1-154510,14 |
|
| |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
|
| |
Abstract |
We study the structure and phase behavior of fullerene-cubane C60·C8H8 by Monte Carlo simulation. Using a simple potential model capturing the icosahedral and cubic symmetries of its molecular constituents, we reproduce the experimentally observed phase transition from a cubic to an orthorhombic crystal lattice and the accompanying rotational freezing of the C60 molecules. We elaborate a scheme to identify the low-temperature orientations of individual molecules and to detect a pattern of orientational ordering similar to the arrangement of C60 molecules in solid C60. Our configuration of orientations supports a doubled periodicity along one of the crystal axes. |
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
New York, N.Y. |
Editor |
|
|
| |
Language |
|
Wos |
000265486300036 |
Publication Date |
2009-04-22 |
|
| |
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 |
8 |
Open Access |
|
|
| |
Notes |
|
Approved |
Most recent IF: 2.965; 2009 IF: 3.093 |
|
| |
Call Number |
UA @ lucian @ c:irua:77258 |
Serial |
2519 |
|
| Permanent link to this record |
| |
|
| |
|
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 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Verberck, B.; Popov, V.N.; Nikolaev, A.V.; Lamoen, D. |
|
| |
Title |
Valence electronic charge density of distorted C60-monomers in polymerized KC60 and RbC60 |
Type |
A1 Journal article |
| |
Year |
2004 |
Publication |
The journal of chemical physics |
Abbreviated Journal |
J Chem Phys |
|
| |
Volume |
121 |
Issue |
|
Pages |
321 |
|
| |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
|
| |
Abstract |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
New York, N.Y. |
Editor |
|
|
| |
Language |
|
Wos |
000222112100035 |
Publication Date |
2004-06-16 |
|
| |
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 |
7 |
Open Access |
|
|
| |
Notes |
|
Approved |
Most recent IF: 2.965; 2004 IF: 3.105 |
|
| |
Call Number |
UA @ lucian @ c:irua:47380 |
Serial |
3830 |
|
| Permanent link to this record |
