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Title
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Orientational order and disorder in solid : theory and diffraction experiments
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Author
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Abstract
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| 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. |
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Language
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English
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Source (journal)
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Acta crystallographica: section A: foundations of crystallography. - Copenhagen
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Publication
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Copenhagen
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1995
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ISSN
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0108-7673
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DOI
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10.1107/S0108767394013280
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Volume/pages
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51
:3
(1995)
, p. 365-374
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ISI
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A1995RB59400018
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Full text (Publisher's DOI)
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