Size-Disparity Anharmonicity
A new analytic procedure which allows one to recognize anharmonic behavior at any temperature is applied to the measured heat capacity of LiCl. The results imply that LiCl experiences an anomalous anharmonicity similar to that found in the so-called quantum solids. This anharmonicity corresponds to an apparent increase of the lattice frequencies with increasing temperature and can be understood in terms of the excess interstitial volume around the positive ions. These size-disparity arguments lead one to expect this anomalous behavior in a number of solids.