Ab initio perturbed ion calculations were performed for the cubic, orthorho
mbic, hexagonal, and monoclinic phases of PbF2. A complete characterization
of these phases was achieved in terms of the potential energy surfaces, th
e equations of state, and the phase-transition pressures. Thermal effects w
ere included via a quasiharmonic nonempirical Debye model. The internal par
ameters of the unit cell of each phase were reoptimized at each volume to g
enerate the energy surface. The calculated results are in good agreement wi
th the experimental data available for the cubic and orthorhombic phases. T
he results predict the hexagonal phase to be the high-pressure post-cotunni
te structure for PbF2, since the monoclinic phase is seen to collapse into
the hexagonal phase during the optimization at high pressures.