Specific heats and lattice dynamics of cuprous halides

The specific heats $C_p\mathrm{}\left(T\right)\mathrm{}$ of CuCl, CuBr, and CuI were measured by the adiabatic calorimetric technique. The corresponding Debye temperature for each crystal is given and a comparison between the results is drawn. The room-temperature phonon dispersion relations for these cystals are fitted by a nine-parameter shell model which gives good fits to CuBr and CuI and a fair fit to CuCl. These model calculations are used to compute $C_v\mathrm{}\left(T\right)\mathrm{}$ for the three cuprous halides and the calculated results are compared with experiment. The agreement is good for the range of $T>\mathrm{}30\mathrm{}°$K and less so for $T<\mathrm{}30\mathrm{}°$K where discrepancies are to be expected due to anharmonicity that affects the theoretical results. For CuCl we also obtain the Grüneisen parameter $\gamma \mathrm{}\left(T\right)\mathrm{}$ using thermal expansion data.