Pressure and temperature derivatives of the elastic constants of caF 2 and BaF 2

Abstract

The elastic constants and their pressure and temperature derivatives were measured by the ultrasonic pulse-echo technique for CaF 2 and BaF 2 at 195° and 298°K. The elastic constants and the pressure derivatives were analyzed in terms of a dipole shell model due to Axe. The Gruneisen parameter in the low temperature limit was calculated and found to compare favorably with the Gruneisen parameter determined from thermodynamic data. The explicit temperature dependencies of the normal mode frequencies for the non-dispersive acoustic modes were calculated. The ultrasonic equation of state is determined and compared with Bridgman's compression data.