Ground State Properties of Newly Discovered Superconductor :MgB2 : an ab initio Hartree-Fock,and Density Functional Studies

Abstract

The ground state properties of magnesium diboride (MgB2), a binary compound known since 1950s but very recently discovered as a superconductor, are investigated in the present study. We use here ab initio Ha11ree-Fock Linear Combination of Atomic Orbitals (HF-LCAO) method. Ha11ree-Fock (HF) and density functional theory (DFT) options of the method have been applied for the study of energy, elastic constants, bulk modulus, band structure, density of states (DOS) and electric field gradient (EFG) for MgB2 both in equilibrium and under pressure. The zero pressure bulk modulus, pressure derivative of bulk modulus and their in- and out-of­plane linear values are calculated and analyzed. The analysis of the evaluated parameters reveals the diversity in bonding interactions. The diboride is found to be characterized by moderately sizable anisotropy of compressibilities, which is smaller than cuprates, but larger than many 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 Fermi energy. --------