Ab initio calculations on superconducting metal-hydride and perovskites for energy applications

Abstract

Superconducting hydrides and photovoltaic perovskites for energy applications are studied by means of the density functional theory-based calculations. First of all, the new decoration of Mg0.5Ca0.5H6 is confirmed thermodynamically stable over the pressures ranging from 200 to 400 GPa. The electronic properties reveal the possibility for this very material of becoming a superconductor under pressures. As a result, by performing electron-phonon coupling (EPC) calculations, Mg0.5Ca0.5H6 is found to superconduct at a maximum critical temperature of 288 K at 200 GPa, which completely exceeds those of its parent compounds, i.e. MgH6 and CaH6. Secondly, the van de Waals (vdW) interaction is incorporated in the DFT calculations to determine the preferred orientations of the organic CH3NH3 (MA) cation embedded at the centre of MAPbI3 perovskite. The well-developed vdW-DF-cx functional is selected to evaluate the total energies of different MA dipolar configurations in a cubic supercell of MAPI under pressures. Finally, due to its lead-free contents, MABiSeI2 perovskite is applied the Eulerian angles to its MA cation is three-dimensional space to determine its corresponding total energies. The complexity of angle-energy relationship is alleviated with the help of a high-fidelity simulation based on deep learning.