Specific heats and lattice dynamics of cuprous halides

Abstract

The specific heats ${C}_{p}(T)$ 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 ${C}_{v}(T)$ for the three cuprous halides and the calculated results are compared with experiment. The agreement is good for the range of $T>30\ifmmode^\circ\else\textdegree\fi{}$K and less so for $T<30\ifmmode^\circ\else\textdegree\fi{}$K where discrepancies are to be expected due to anharmonicity that affects the theoretical results. For CuCl we also obtain the Gr\"uneisen parameter $\ensuremath{\gamma}(T)$ using thermal expansion data.