材料期刊网

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 OK) and Gibbs free energy G* (at 300K), we find that the phase transition pressure from the lace-centred cubic (fcc) structure to the orthorhombic structure is 11.40 GPa and 9.33 GPa at 0 K and 300 K, 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.