PHASE-DIAGRAM AND THERMODYNAMIC PROPERTIES OF SOLID MAGNESIUM IN THE QUASI-HARMONIC APPROXIMATION

Using a family of volume-dependent interatomic pair potentials derived from first principles, we calculate phonon properties and thermodynam ic functions in the quasiharmonic approximation for the hcp and bcc ph ases of Mg over a wide range of volume and temperature. At atmospheric pressure, the calculated hcp phonon-dispersion curves and thermodynam ic properties agree well with experiment. The pressure dependence of t he Raman-active transverse-optical phonon mode also agrees well with v ery recent measurements. At high pressure, the temperature dependence of the hcp-bcc phase line is predicted, with values of the transition pressure ranging from 52 GPa at zero temperature to about 28 GPa at 10 00 K.