Anharmonic Effects on the Specific Heat and Elastic Constants

3 Anharmonic Effects on the Specific Heat and Elastic Constants 

We have derived an expression for the specific heat of the anharmonic linear chain which is valid at high temperatures (5.65) due to anharmonicity, Cj (T) is proportional to T at high temperatures. The same result also applies for the specific heat c (T) of three-dimensional crystals [5.31,32]. As in (5.65), the coefficient of proportionality is determined by the third and fourth-order anharmonic coupling constants. In addition, the generalization of the expression (5.67) for Cj - Cj to cubic crystals is straightforward, namely, 

In Sect.3.6, we established relations between the elastic constants and the atomic force constants (3.116,128,137). In Sect.5.2.2, we obtained the result that due to anharmonicity, the atomic force constants depend on temperature and pressure, (5.54,55). We therefore expect that the elastic con- 

Temperature dependence of the elastic constants (in units of dyn/cm2) of LiCl [5.33] 

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