We have performed first-principles total energy calculations for solid Ar and Kr to study phase transitions under high pressure. We used relativistic, nonlocal, norm-conserving pseudopotentials with a plane wave basis in solving the Kohn-Sham equations within the local density approximation for fcc, hcp, and bcc structures of Ar and Kr. Within the volume range we have studied (V/${\mathit{V}}_0$ = 1.0 to 0.1, where ${\mathit{V}}_0$ is the observed volume at 1 atm and 0 K), both Ar and Kr undergo a phase transition from the fcc to the hcp structure at pressures of about 220 and 130 GPa, respectively, and the insulator-metal transition should occur around 510 GPa (Ar) and 310 GPa (Kr) in the hcp phase.

• Received 19 July 1995

DOI:https://doi.org/10.1103/PhysRevB.52.15165