Ab initio thermoelasticity of magnesium

The elastic moduli of magnesium (Mg) have been evaluated as functions of pressure and temperature through the use of fluctuation formulas and Monte Carlo simulation. The simulations employ ab initio interatomic potentials for Mg derived from generalized pseudopotential theory and used previously to predict the temperature-pressure phase diagram of this metal to 60 GPa [Phys. Rev. B 51, 5609 (1995)]. Comparison with experimental data at ambient pressure and low temperature shows that the calculated elastic constants agree with the measured values to within about 10%. The temperature and pressure derivatives of the moduli are likewise closely reproduced. Theoretical results are also given for high pressures (to 40 GPa) and high temperatures (to 1500 K) in the relevant hcp and bcc crystal structures. No elastic anomalies are seen on approaching the predicted hcp-bcc phase transition. Implications for the detection of this transition in shock experiments are discussed.