A magnetic model for the demonstration of phase transitions and excitations in molecular crystals
作者:
C. Nöldeke,
W. Press,
A. Hüller,
期刊:
American Journal of Physics
(AIP Available online 1991)
卷期:
Volume 59,
issue 3
页码: 260-269
ISSN:0002-9505
年代: 1991
DOI:10.1119/1.16574
出版商: American Association of Physics Teachers
关键词: LATTICE DYNAMICS;MOLECULAR CRYSTALS;ORDER−DISORDER TRANSFORMATIONS;MEAN−FIELD THEORY;EXCITATION;PHONONS
数据来源: AIP
摘要:
A magnetic model for the demonstration of structural properties and the lattice dynamics of molecular crystals is presented. It is used to visualize an orientational order–disorder phase transition. The orientational order of the low‐temperature phase observed on the model is also obtained from a mean field calculation. A simple theory for harmonic excitations of the model is presented, which gives the dispersion relation for an infinite crystal. The frequencies of the observed resonances of the finite model are compared with the results of a numerical eigensystem analysis and with the dispersion relation. Within the limitations given by the construction of the model the results are in rather good agreement.
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