Equation of state and elastic properties of beryllium from first principles calculations

The electronic and structural properties of beryllium were investigated under high pressure using first principle pseudopotential calculations within the generalized gradient approximation (GGA). Our results including pressures, elastic constants, Debye temperatures for two crystal structures (alpha hexagonal close packed and beta body-centred cubic) are compared with the experimental and other theoretical data over a wide density range. Calculated phonon spectra allow us to explain the anomalous behavior of the hcp-bcc transition under pressure. An equation of state (EOS) for the hcp phase at finite temperatures is derived taking into account the anharmonicity effects of thermal lattice vibrations. The resulting 300 K isotherm and Hugoniot curve, as well as the evolution of the shear modulus under pressure and temperature, are in good agreement with available experimental and theoretical data.