“Microscopic theory of orientational disorder and lattice instability in solid C70”. Callebaut AK, Michel KH, Physical review : B : condensed matter and materials physics 52, 15279 (1995). http://doi.org/10.1103/PhysRevB.52.15279
Abstract: We have developed a microscopic theory which describes the orientational dynamics of C-70 molecules and its coupling to lattice displacements in the face-centered-cubic phase of C-70 fullerite. The single-molecule orientational density distribution in the disordered phase is calculated. The ferroelastic transition to the rhombohedral phase is investigated. The discontinuity of the orientational order parameter at the phase transition is calculated. It is found that the transition leads to a stretching of the primitive unit cell along a [111] cubic direction. A softening of the elastic constant c(44) at the transition is predicted.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.736
Times cited: 20
DOI: 10.1103/PhysRevB.52.15279
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“Microscopic theory of quadrupolar oredring in TmTe”. Nikolaev AV, Michel KH, Physical review : B : condensed matter and materials physics 63, 1 (2001). http://doi.org/10.1103/PhysRevB.63.104105
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 7
DOI: 10.1103/PhysRevB.63.104105
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“Microscopic theory of the rhombohedral phase and transition to the monoclinic phase of solid C70”. Nikolaev AV, Michel KH, Physical review : B : condensed matter and materials physics 54, 12733 (1996). http://doi.org/10.1103/PhysRevB.54.12733
Abstract: Starting from a model of microscopic interactions between C-70 molecules, we have developed a theory which describes the orientational dynamics and its coupling to lattice displacements in the rhombohedral phase of C-70 fullerite. The Landau free energy is calculated. We obtain a first-order phase transition to a monoclinic structure with the space group P2(1)/m. The transition is driven by the condensation of orientational quadrupoles at the F point of the Brillouin zone of the rhombohedral lattice. We find no evidence that the monoclinic structure is connected with the freezing in of orientations around the fivefold molecular axis. We calculate the lattice strains that are associated with the transition to the monoclinic structure. The theory is compared with a range of experimental data on the phase transition.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.736
Times cited: 5
DOI: 10.1103/PhysRevB.54.12733
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“Microscopic theory of thermoelastic phenomena and pressure dependence in solid C60”. Lamoen D, Michel KH, Physical review : B : condensed matter and materials physics 48, 807 (1993). http://doi.org/10.1103/PhysRevB.48.807
Abstract: A microscopic theory for the coupling of molecular orientations with acoustic lattice displacements is proposed. The relevant interaction is quadratic in the orientational-order-parameter variables and linear in longitudinal strains. The coupling is evaluated for a complex molecular structure. The intermolecular potential is obtained from interaction centers placed at nuclei and at the centers of interatomic bonds. The free energy is derived and the experimental consequences of the theory are studied. The Clausius-Clapeyron equation for orientational melting is obtained. The theory explains the decrease of the lattice constant at the first-order phase transition and the increase of the transition temperature with applied pressure.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.736
Times cited: 32
DOI: 10.1103/PhysRevB.48.807
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“Symmetry lowering at the structural phase transitions in NpO2 and UO2”. Nikolaev AV, Michel KH, Physical review : B : condensed matter and materials physics 68, 054112 (2003). http://doi.org/10.1103/PhysRevB.68.054112
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.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 15
DOI: 10.1103/PhysRevB.68.054112
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“Theoretical model for the structural phase transition at the metal-insulator transition in polymerized KC60”. Verberck B, Nikolaev AV, Michel KH, Physical Review B 66, 165425 (2002). http://doi.org/10.1103/PhysRevB.66.165425
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.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 10
DOI: 10.1103/PhysRevB.66.165425
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“Stabilization of mercury-based superconductors by foreign cations”. Raveau B, Michel C, Hervieu M, Van Tendeloo G, Maignan A, Annales de chimie (1914)
T2 –, 4th North-African Materials Science Symposium (JMSM 94), NOV 23-24, 1994, CASABLANCA, MOROCCO 19, 487 (1994)
Abstract: The recently discovered superconducting mercury-based cuprates HgBa2Can-1CunO2n+2+delta have proved difficult to synthesize as single phases and are sensitive to environment (CO2, moisture). The present paper gives an overview of new series mercury based superconductors, whose stabilisation is based on the fact that a foreign cation with a higher valency than Hg(II) must be introduced in the mercury layers, in order to fill up partially the oxygen vacancies of these layers. By this method, several new series of superconductors involving strontium instead of barium with critical temperatures ranging from 27 K to 95 K have been isolated : Hg0.5Bi0.5Sr2-xLaxCuO4+delta, Hg(0.5)Bi(0.5)Sr(2)Ca(1-x)R(x)Cu(2)O(6+delta) (R Y, Nd, Pr), Pb0.7Hg0.3Sr2-xLaxCuO4+delta, Pb(0.7)Hg(0.3)Sr(2)Ca(1-x)R(x)Cu(2)O(6+delta) (R = Y, Nd) Hg(1-x)Pr(x)Sr(2)A(1-x')Pr(x') Cu2O6+delta (A = Sr, Ca), Pb0.7Hg0.3Sr2Cu2CO3O7 and Hg1-xCrxSr2CuO4+delta. The behaviour of the praseodymium cuprates that exhibit a rather sharp transition and reach a Tc of 85 K is especially discussed. A method to synthesize new ''Ba-Hg'' superconducting cuprates with the 1212 structure at normal pressure with a Tc up to 110 K is also presented.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 2
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“Coupling of orientational and translational modes in solid C60 and C70”. Lamoen D, Michel KH, Phase transitions 67, 789 (1999). http://doi.org/10.1080/01411599908224511
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.06
Times cited: 2
DOI: 10.1080/01411599908224511
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“Orientational order and disorder in solid C60 : theory and diffraction experiments”. Michel KH, Lamoen D, David WIF, Acta crystallographica: section A: foundations of crystallography 51, 365 (1995). http://doi.org/10.1107/S0108767394013280
Abstract: Starting from a microscope model of the intermolecular potential, a unified description is presented of the Bragg scattering law in the orientationally disordered and in the ordered phase of solid C-60. The orientational structure factor is expanded in terms of symmetry-adapted surface harmonics. The expansion coefficients are calculated from theory and compared with experiment Their temperature evolution is studied in the disordered phase at the 260 K transitions and in the ordered phase. In the ordered phase, new results from high-resolution neutron powder diffraction are given. In the disordered phase, space group Fm $($) over bar$$ 3m, the reflections have A(1g) symmetry; in the ordered phase, space group Pa $$($) over bar 3, reflections of T-2g symmetry appear and in addition the A(1g) reflections are renormalized. The orientational density distribution is calculated. The effective crystal-field potential is constructed, its temperature evolution in the ordered phase is studied and related to the occurrence of an orientational glass.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.307
Times cited: 14
DOI: 10.1107/S0108767394013280
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“Mercator maps of orientations of a C60 molecule in single-walled nanotubes with distinct radii”. Michel KH, Verberck B, Nikolaev A, AIP conference proceedings 786, 69 (2005)
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.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
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“Orientational charge density waves and the metal-insulator transition in polymerized KC60”. Verberck B, Nikolaev AV, Michel KH, AIP conference proceedings 723, 339 (2004)
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.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
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“Many electron- and hole terms of molecular ions C60n\pm”. Nikolaev AV, Michel KH, Coupling In Chemistry And Physics 44, 305 (2003). http://doi.org/10.1016/S0065-3276(03)44019-7
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.196
Times cited: 1
DOI: 10.1016/S0065-3276(03)44019-7
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“Interpreting technical evidence from spectral imaging of paintings by Edouard Manet in the Courtauld Gallery”. Amato SR, Burnstock A, Cross M, Janssens K, Rosi F, Cartechini L, Fontana R, Dal Fovo A, Paolantoni M, Grazia C, Romani A, Michelin A, Andraud C, Tournie A, Dik J, X-ray spectrometry
T2 –, MA-XRF Workshop on Developments and Applications of Macro-XRF in, Conservation, Art, and Archeology, SEP 24-25, 2017, Trieste, ITALY 48, 282 (2019). http://doi.org/10.1002/XRS.2828
Abstract: The paintings by edouard Manet in The Courtauld Gallery Dejeuner sur l'herbe (1863-68), Marguerite de Conflans en Toilette de Bal (1870-1880), Banks of the Seine at Argenteuil (1874), and A Bar at the Folies-Bergere (1882) were investigated for the first time using a range of non-invasive in situ analyses. The aims of the study were to investigate the painting techniques and materials used for this group of works and to critically evaluate the technical evidence derived from the integrated use of imaging techniques and portable spectroscopic methods in this context. The paintings were investigated by means of macro X-ray fluorescence (MA-XRF), reflection spectral imaging, portable UV-Vis-NIR spectroscopy, portable Raman spectroscopy, and reflection FTIR. MA-XRF and reflection spectral imaging allowed visualising elements in the compositions that were not visible using traditional methods of technical study. For example, MA-XRF analysis of Dejeuner sur l'herbe revealed elements of the development of the composition that provided new evidence to consider its relationship to other versions of the composition. The study also highlighted questions about the interpretation of elemental distribution maps and spectral images that did not correspond to the reworking visible in X-radiographs. For example, in A Bar at the Folies-Bergere Manet made numerous changes during painting, which were not clearly visualised with any of the techniques used. The research has wider implications for the study of Impressionist paintings, as the results will support technical studies of works by other artists of the period who used similar materials and painting methods.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.298
DOI: 10.1002/XRS.2828
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“Electronic structure and electric quadrupoles of a polymerized chain in solid AC60”. Nikolaev AV, Michel KH, Solid state communications 117, 739 (2001). http://doi.org/10.1016/S0038-1098(01)00017-5
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.554
Times cited: 10
DOI: 10.1016/S0038-1098(01)00017-5
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“A mercury-based “1201-0201&rdquo, intergrowth HgBa2La2Cu2O8+x: a 53K superconductor”. Huvé, M, Martin C, Van Tendeloo G, Maignan A, Michel C, Hervieu M, Raveau B, Solid state communications 90, 37 (1994)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.897
Times cited: 7
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“A mercury based cuprate with the “2212&rdquo, structure: Hg2-x(Cu,Pr)xBa2PrCu2O8-\delta”. Martin C, Hervieu M, Van Tendeloo G, Goutenoire F, Michel C, Maignan A, Raveau B, Solid state communications 93, 53 (1995)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.897
Times cited: 6
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“Substitution of mercury for thallium in the 2223 cuprate: the 130K superconductor Tl1.6Hg0.4Ba2Cu3O10-x”. Goutenoire F, Maignan A, Van Tendeloo G, Martin C, Michel C, Hervieu M, Raveau B, Solid state communications 90, 47 (1994)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.897
Times cited: 16
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“Translation-rotation coupling, phase transitions and elastic phenomena in orientationally disordered crystals”. Lynden-Bell RM, Michel KH, Reviews of modern physics 66, 721 (1994). http://doi.org/10.1103/RevModPhys.66.721
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 29.604
Times cited: 128
DOI: 10.1103/RevModPhys.66.721
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“Anisotropic packing and one-dimensional fluctuations of C60 molecules in carbon nanotubes”. Michel KH, Verberck B, Nikolaev AV, Physical review letters 95, 185506 (2005). http://doi.org/10.1103/PhysRevLett.95.185506
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.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 8.462
Times cited: 40
DOI: 10.1103/PhysRevLett.95.185506
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“Bond geometry and phase transition mechanism of H-bonded ferroelectricity”. Bussmann-Holder A, Michel KH, Physical review letters 80, 2173 (1998). http://doi.org/10.1103/PhysRevLett.80.2173
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 8.462
Times cited: 81
DOI: 10.1103/PhysRevLett.80.2173
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“Theory of distinct crystal structures of polymerized fullerides AC60, A=K, Rb, Cs: the specific role of alkalis”. Michel KH, Nikolaev AV, Physical review letters 85, 3197 (2000). http://doi.org/10.1103/PhysRevLett.85.3197
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 8.462
Times cited: 16
DOI: 10.1103/PhysRevLett.85.3197
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“Microscopic theory of orientational disorder and the orientational phase transition in solid C60”. Michel KH, Copley JRD, Neumann DA, Physical review letters 68, 2929 (1992). http://doi.org/10.1103/PhysRevLett.68.2929
Abstract: We have developed a microscopic theory which describes the orientational dynamics of C60 molecules in the face-centered-cubic phase of C60 fullerite. The molecular interaction potential and the crystal-field potential are formulated in terms of symmetry-adapted rotator functions. The phase transition to the Pa3BAR structure is driven by an active multipolar mode of T2g symmetry belonging to the l = 10 manifold. The Birman criterion is satisfied. The transition is found to be of first order.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 7.512
Times cited: 94
DOI: 10.1103/PhysRevLett.68.2929
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“A new cuprate with mercury bilayers : the “2222&rdquo, oxide Hg2-xMxBa2Pr2Cu2O10-\delta (M= Cu,Pr)”. Huve M, Martin C, Maignan A, Michel C, Van Tendeloo G, Hervieu M, Raveau B, Journal of solid state chemistry 114, 230 (1995). http://doi.org/10.1006/jssc.1995.1033
Abstract: A ''2222'' cuprate with mercury bilayers (Hg1.5Cu0.2Pr0.3)Ba2Pr2Cu2O10-delta, has been synthesized for the first time. It crystallizes in the P4/nmm space group with a = 3.9072(1) Angstrom and c = 17.219(1) Angstrom. The powder XRD and HREM studies of this new cuprate show that its structure consists of an intergrowth of double pyramidal (oxygen-deficient perovskite) copper layers, with double fluorite-type layers and distorted triple rock salt layers (mercury bilayers). The structure of this phase can be deduced from that of the ''2212'' mercury cuprate (Hg1.5Cu0.2Pr0.3)Ba2PrCu2O8-delta by the introduction of one additional [PrO2]infinity fluorite layer. The regular stacking of the metallic layer and the uniform cationic distribution in the mercury bilayers are remarkable features of this cuprate. The stabilization of the mercury bilayers by praseodymium and the absence of superconductivity are discussed. (C) 1995 Academic Press, Inc.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.133
Times cited: 6
DOI: 10.1006/jssc.1995.1033
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“Structural aspects of Bi2-xPbxSr3.5Cu2(CO3)O8-\delta for 0\leq x\leq0.75 : an electron-microscopy study”. Zhang XF, Van Tendeloo G, Amelinckx S, Pelloquin D, Michel C, Hervieu M, Raveau B, Journal of solid state chemistry 113, 327 (1994). http://doi.org/10.1006/jssc.1994.1378
Abstract: The structure and defect structure of Bi2-xPbxSr3.5Cu2 (CO3)O8-delta compounds with 0 less-than-or-equal-to x less-than-or-equal-to 0.75 are carefully investigated by electron diffraction and high-resolution electron microscopy. All compounds have an orthorhombic structure with a almost-equal-to b almost-equal-to 5.4 angstrom and c almost-equal-to 39.5 angstrom. The length of the b-axis decreases monotonically with increasing x. The space group for the basic structure is Abm2. The structure can be considered as an intergrowth of Bi2Sr2CuO6 lamellae with Sr2CuO2 (CO3) lamellae along the c-axis. CO3 groups behave as bridges connecting the CuO6 octahedra. In the x = 0 compound the carbon atoms are shifted away from their symmetry positions; the orientational ordering of the CO3 groups (or the carbon shift) in successive CO planes alternates along +b and -b. Typical Bi-type and Pb-type modulations are found along the b-axis up to a Pb content x = 0.5. Electron beam irradiation destroys the ordering of the CO3 groups and alters the modulated structure. (C) 1994 Academic press, inc.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.133
Times cited: 8
DOI: 10.1006/jssc.1994.1378
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“Synthesis and characterization of mercury based “1222&rdquo, cuprates (Hg1-xMx)(Sr,Ba)2Pr2Cu2O9-\delta (M = Pr, Pb, Bi, Tl)”. Hervieu M, Van Tendeloo G, Michel C, Martin C, Maignan A, Raveau B, Journal of solid state chemistry 115, 525 (1995). http://doi.org/10.1006/jssc.1995.1169
Abstract: Five new layered cuprates, with a 1222-type structure, have been synthesized according to the formula (Hg(1-x)M(x))(Sr,Ba)(2) Pr2Cu2O9-delta with M = Pr, Pb, Pi, and Tl. They crystallize in a tetragonal cell with a approximate to a(p) and c approximate to 29.5 Angstrom; their structure consists in a triple intergrowth of oxygen-deficient perovskite, rock-salt-and fluorite-type layers. They are characterized by a mixed [Hg(1-x)M(x)O(1-delta)] layer in the rock-sail-type slice. The ED and HREM studies show that Tl, Bi, and Pb are statistically distributed in the mixed [Hg(1-x)M(x)O(1-delta)] layer, contrary to Pr which involves an ordering phenomenon along a. Different stacking defects are observed and discussed as well as the cleavage mode of the crystals. (C) 1995 Academic Press, Inc.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.133
Times cited: 5
DOI: 10.1006/jssc.1995.1169
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“Structural characteristics of the 40K superconductor Bi2Sr5Cu3(CO3)2O10: a HREM study”. Hervieu M, Pelloquin D, Michel C, Van Tendeloo G, Raveau B, Journal of solid state chemistry 112, 139 (1994)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.133
Times cited: 5
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“Polarizability induced cooperative proton ordering, coexistence of order/disorder and displacive dynamics and isotope effects in hydrogen-bonded systems”. Bussmann-Holder A, Dalal N, Michel KH, The journal of physics and chemistry of solids
T2 –, Williamsburg Workshop on Ferroelectrics 99, JAN 31-FEB 03, 1999, WILLIAMSBURG, VIRGINIA 61, 271 (2000). http://doi.org/10.1016/S0022-3697(99)00292-9
Abstract: Despite the general belief that hydrogen-bonded ferro- and antiferroelectrics undergo a pure order/disorder transition at the structural instability, new NMR data and a new theoretical concept yield convincing evidence that a pronounced displacive component is present in these systems, which modifies substantially the temperature dependencies of the tunnel and lattice mode frequencies. The experiments and their interpretation are presented. (C) 1999 Elsevier Science Ltd. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.059
Times cited: 8
DOI: 10.1016/S0022-3697(99)00292-9
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“Charge transfer and polymer phases in AC60 (A=K, Rb, Cs) fullerides”. Nikolaev AV, Prassides K, Michel KH, The journal of chemical physics 108, 4912 (1998). http://doi.org/10.1063/1.475900
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.965
Times cited: 14
DOI: 10.1063/1.475900
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“Crystal field, orientational order, and lattice contraction in solid C60”. Lamoen D, Michel KH, The journal of chemical physics 101, 1435 (1994). http://doi.org/10.1063/1.467768
Abstract: A model of the intermolecular potential in solid C-60, which is based on Born-Mayer repulsions, van der Waals attractions, and electrostatic multipoles, is presented. The potential is expanded in terms of multipolar rotator functions. The orientation-orientation interaction and the crystal field are calculated. The orientational phase transition to the Pa3 phase is studied with the methods of statistical mechanics. The discontinuity of the order parameter at the transition and the temperature evolution of the order parameter are calculated. The lattice contraction at the phase transition is evaluated. The influence of the lattice contraction on the crystal field and on the orientational order is studied.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.952
Times cited: 39
DOI: 10.1063/1.467768
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“Crystal structures of polymerized fullerides AC60, A=K, Rb, Cs, and alkali-mediated interactions”. Verberck B, Michel KH, Nikolaev AV, The journal of chemical physics 116, 10462 (2002). http://doi.org/10.1063/1.1475745
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.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.965
Times cited: 12
DOI: 10.1063/1.1475745
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