Ab initio study of pressure induced phase transition, structural and electronic structure properties of superconducting perovskite compound GdBa2Cu3O7-x

Abstract

The structural, phase transition and the electronic structure properties (density of state and the band structure) for the ceramic Gadolinium Barium Copper Oxide (GdBa2Cu3O7-x) have been studied using the open source Quantum Espresso code. Ultra soft pseudo potential with generalized gradient approximation (GGA) and local density approximation (LDA) were used to calculate the ground state energy. Optimized lattice parameter and bulk modulus are found from total energy calculations. Phase transition from the orthorhombic to tetragonal phase was found to occur at 219.15 Kbar. At zero pressure the material portrayed a semi-conducting property with a direct band gap of ≈0.78eV occurring near the T point of the Brillouin zone sampling. At high pressure we noted that the decrease in volume resulted to conduction band crossing the Fermi level resulting to overlapping of bands and the material underwent metallization.