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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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