Phase Transition and Melting Curves of Calcium Fluoride via Molecular Dynamics Simulations

The phase transition and melting curves of CaF₂ are investigated by using the general utility lattice programme (GULP) via the shell model with molecular dynamics method. By calculating the entropy H (at 0K) and Gibbs free energy G* (at 300K), we find that the phase transition pressure from the face-centred cubic (fcc) structure to the orthorhombic structure is 11.40GPa and 9.33GPa at 0K and 300K, respectively. The modified melting point of the fcc CaF₂ is in the range of 1650--1733K at 0GPa. All these results are well consistent with the available experimental data and other theoretical results. We also obtain that the melting temperature of high pressure phase is 990--1073K at 10GPa. Moreover, the temperature dependences of the elastic constants C_ij, bulk module B and shear module G are also predicted.