Effect of hydrostatic pressure on the elastic constants of cubic PbF2

Abstract
The adiabatic elastic stiffness moduli of fluorite-structure PbF2 have been determined at hydrostatic pressures up to 3 kbar by means of ultrasonic velocity measurements at 296 K. All moduli increase linearly with pressure indicating that the impending transformation to the orthorhombic structure at 4 kbar is not due to softening of long-wavelength acoustic modes. It is found that a simple lattice-dynamical shell model fails to account for the pressure dependences of the moduli. Possible reasons are suggested.