First-principles study of solid Ar and Kr under high compression

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 fee, hcp, and bcc structures of Ar and Kr. Within the volume range we have studied (V/V-o = 1.0 to 0.1, where V-o is the observed volume at 1 atm and 0 K), both Ar and Kr undergo a phase transition from the fee 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.