Atomistic Simulation of the Equation of State of SrF 2 Using Electron Gas Interionic Potentials

We have determined the equation of state (EOS) of SrF 2 in the cubic (C1, Fm3m ) and orthorhombic (C23, Pbnm ) phases using Electron Gas Interionic Potentials (EGIP) that incorporate many-body energy components. Thermal effects are included by means of a quasi-harmonic Debye model. The zero pressure unit cell length ( a 0 ), lattice energy ( E latt ), bulk modulus ( B 0 ), and EOS of the C1 phase are predicted in good agreement with the observed data. Moreover, the computed EOS satisfy very well the empirical Vinet EOS. Fittings of m / m 0 m p data ( m = a, b, c ) to linear forms of the Vinet EOS reveal that SrF 2 (C23) is more compressible along the b and c axes than along the a direction. Finally, the {\rm C1}\rightleftharpoons {\rm C23} transition is predicted to occur at p t =3.92 GPa, which is between the observed direct ( p t =5.0 GPa) and reverse C1 ( p t =1.7 GPa) phase transitions.