Density functional theory calculations on EOS and phase stability of beryllium

Our current equation of state (EOS) for Beryllium is based on experimental data and empirical models. This construction does not fully constrain the resulting EOS, and recently uncovered experimental results in the literature show slight disagreement with the established EOS of Be. To address this disagreement we have calculated the cold curve and the phonons for Be in the hexagonal close-packed (hcp) structure using density functional theory. From these we extract the thermal expansion and the Grüneisen parameter; the former agrees well with experiment, the latter leads to a slight adjustment of the EOS. The same calculations for Be in the body-centered cubic (bcc) structure leads to a predicted structural phase transition from hcp to bcc at a pressure of 415 GPa (at 0 K) that decreases to 360 GPa (near the melting temperature T_m=1560 K).