Calculated elastic and electronic properties of MgB$_2$ at high pressures

Abstract

The effect of high pressure on structural and electronic properties of the novel superconductor MgB$_2$ has been calculated using the full-potential linearized augmented-plane-wave method. Despite the layered crystal structure of MgB$_2$ nearly isotropic compression (bulk modulus $B_0=140.1(6)$ GPa) is found with only a 1.2% decrease of the $c/a$ ratio at 10 GPa. The effect of pressure on the critical temperature has been estimated on the basis of BCS theory and good agreement with experimental data is found. Our results suggest that the primary causes for the reduction of $T_c$ are a decrease of the density of electronic states at the Fermi energy and an increase of the zone-center phonon frequencies.