First-principles study of phase transition of tin and lead under high pressure

The phase transitions of Sn and Pb under high pressure are investigated theoretically using the first-principles pseudopotential method. The calculated results show that for Sn the sequence of phase transitions is alpha-Sn -> beta-Sn -> bct -> bcc under high pressure while hcp-Sn is not observed up to 200 GPa, which is in good agreement with experiments. In addition, for Pb the calculated results indicate that Pb can undergo two phase transitions under high pressure: one is the phase transition from fcc to the hcp structure at a pressure of 16 GPa and the other is the phase transition from hcp to the bcc structure at a pressure and volume changes during the phase transformation are consistent with the experimental values.