Temperature dependence of lattice energy of fluorite type AB₂ crystals, alkaline earth oxides and heavy metal halides – Evaluation from sound velocity data

Abstract

Lattice energies of CaF₂, SrF₂, BaF₂, CdF₂, EuF₂, MgO, SrCl, AgCl and TlBr at different temperatures have been evaluated making use of single crystal elastic constant data and employing Kudriavtsev’s theory which relates the lattice energy of the crystal, <i style="">U</i>, with mean sound velocity, <i style="">u</i>_m, in the crystal. The lattice energies of both MgO and SrO decrease with increase in temperature and the variations are parabolic and similar. The lattice energies of AgCl and TlBr vary with temperature parabolically up to 80 K and thereafter linearly up to 300 K. The results are explained in terms of the structure of the crystals, mutual interaction of the ions and anharmonic effects associated with as a function of temperature.