Effect of Frenkel defects on the high-pressure phase transitions in PbF2 and SrCl2

Significant curvature has been observed in a plot of transition temperature against transition pressure for the high-pressure cubic-orthorhombic phase transition in both PbF2 and SrCl2 at high temperatures. In the present paper it is shown that the presence of a high equilibrium concentration of Frenkel defects in one phase but not the other phase involved in the transition can provide an explanation for this curvature. A comment is also made on the applicability of the work to AgI and RbAg4I5. © 1981 The American Physical Society.