Calculated elastic and electronic properties of MgB2 at high pressures

The effect of high pressure on structural and electronic properties of the novel superconductor MgB2 has been calculated using the full-potential linearized augmented-plane-wave method. Despite the layered crystal structure of MgB2 nearly isotropic compression (bulk modulus B0=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 it is a combination of increasing phonon frequency and decreasing electronic density of states at the Fermi level which leads to the observed decrease of the critical temperature under pressure.