Atomistic simulation of SrF_{2} polymorphs
Abstract
Electron gas interionic potentials (EGIP) have been developed to determine the equation of state (EOS) of the cubic (C1) and orthorhombic (C23) polymorphs of SrF_{2}, including the thermal effects by means of a quasiharmonic Debye model. The zero pressure cell parameter (a_{0}), lattice energy (E_{latt}), and bulk modulus (B_{0}) of the C1 phase are computed with errors smaller than 1.2%, 1.2%, and 7.1%, respectively. The predicted EOS is in good agreement with the observed data and satisfies the universal Vinet EOS. For the C23 phase, the optimized zerop cell parameters a, b, and c and the six fractional coordinates are reported and the pressure dependence of a/a_{0}, b/b_{0}, and c/c_{0} explored by fitting independent modified Vinet EOS's to the computed data. The analysis reveals a greater compressibility of the C23 phase along the b and c axes than along the a direction. Our calculation predicts the C1⇌C23 equilibrium to occur at p_{tr}=3.92 GPa, which is between the observed values for the C1>C23 (p_{tr}=5.0 GPa) and C23>C1 (p_{tr}=1.7 GPa) phase transitions.
 Publication:

Physical Review B
 Pub Date:
 March 2001
 DOI:
 10.1103/PhysRevB.63.094107
 Bibcode:
 2001PhRvB..63i4107F
 Keywords:

 62.50.+p;
 61.50.Ks;
 64.60.i;
 65.20.+w;
 Highpressure and shock wave effects in solids and liquids;
 Crystallographic aspects of phase transformations;
 pressure effects;
 General studies of phase transitions;
 Thermal properties of liquids: heat capacity thermal expansion etc.