THEORETICAL CHARACTERIZATION OF THE STRUCTURAL, ELECTRONIC AND MECHANICAL PROPERTIES OF SUPERCONDUCTING GdBa2Cu3O7-x

Abstract

The aim of the study was to characteris the GdBa2Cu3O7-x perovskite superconductor with the view knowing the associated properties under different conditions of pressure. The study applied the computational methods to investigate the structural, electronic and mechanical, properties of the GdBa2Cu3O7-x perovskite superconductor and determined how its properties affect the mechanism of superconductivity. With the local the generalized gradient approximation in the frame work of density functional theory using the Quantum espresso code, the ground state properties and equation of state were obtained using the Plane waves. The phenomenon of phase transition studied through pressure induction. The effect of pressure on the band structure, density of states and the partial density of state were also assessed. The orbitals that are responsible for metallization and superconductivity were also computed at varied pressure. The effect holes doping with pressure was also simulated. The BCS theory and the Mc Millan’s equation were used to calculate its superconducting transition temperature at different pressure. Doping with variation of oxygen concentration was done. The phase transition was found to occur at 21.9 GPa. It was found that pressure results to narrowing of the band gap for this material and eventually the material undergoes metallization. The orbital that become predominant at the high superconductivity transition temperature below the pressure of phase transition were; Cu 1d and O 2p from the CuO in the valence band near the Fermi level and the Gd 5p near the Fermi level. The stability criterion was satisfied from the calculated elastic constants. Calculated elastic properties were used to calculate Debye temperature and the maximum value was achived at ~20GP. The underdoped regime, where the holes were smaller compared to the ones at optimum doping, was determined to be below 20 GPa of doping pressure. Optimal doping pressure where was achieved at ~ 20 GPa.. There was a drop in T_C above the pressure of around ~20 GPa, which was considered the overdoping regime. The highest calculated 𝑇𝐶 (max) was ~141.16 K at ~20GPa. With oxygen doping the 𝑇𝐶 (max) was found to be 137.9 K when the value of x was 0.65. the finding of the study can be used to in material design for application