Ab initio investigation of mechanical behaviour of MgB2 superconductor under pressure

We present ab initio calculations of a set of physical properties for the newly discovered MgB2 superconductor. The zero pressure bulk modulus, the pressure derivative of the bulk modulus and their in- and out-of-plane linear values are evaluated. An analysis of the calculated parameters reveals the diversity in bonding interactions. The diboride is characterized by a moderately sizable anisotropy of compressibilites, which is smaller than for cuprates, but larger than for other related diborides. The anisotropic compression is expected to induce different pressure effects on different phonon modes and also to influence the electronic structure at the Fermi energy.