Electronic and structural properties of Magnesium dibo ride using density Functional theory

Abstract

In this thesis, electronic and structural properties of Magnesium diboride (MgB2) is investi gated with the density functional theory by using Quantum EPRESSO Package. The gener alized gradient approximation (GGA) is used to compute the exchange correlation energy. The total energy of Magnesium diboride is computed as a function of cutoff energy and Monk Horst pack grid size. The results show that the total energy per cell is monotonically decreasing with increasing cutoff energy and converged at 70Ry plane wave cutoff energy and the ground state energy has its minimumat-130.58056956 Ry. Thetotal energy of MgB2 percellhasconverged at 11 × 11 ×9k-point grids with a ground state energy of-130.31353522 Ry. Besides, the opti mized lattice constants of bulk MgB2 have been determined to be a = 5.8 Bohr and hence, c = 6.669288 Bohr with respect to our computational calculation. The experimental values of bulk HCP Magnesium diboride are a = 5.808413 Bohr and c = 6.678954 Bohr. The lattice constant determined using DFT calculation is compatible with an experimental result with a relative er ror of 0.00144. Finally, the band structure and density of state of HCP magnesium diboride are computed. The band structure calculation shows that there is overlap between the conduction band and the valance band. This clearly shows that MgB2 is conductor or metal (zero band gap material). The density of state also shows that there is no discontinuity before and after the Fermi Level. The density of state is continuous and there is no an insulating regime.