First-principles calculations to investigate structural, electronic, optical and thermodynamic properties of anti-perovskite compounds X3OI(X = Na, K, Rb)

The stability, electronic, optical and thermodynamic properties of X3OI (X = Na, K, Rb) have been calculated by first principles. The Birch-Murnaghan method was used to fit the optimal lattice constants of the three materials. The results show that the three compounds are stable and the calculated thermodynamic properties show that they conform to Dulong-Petit's law. They absorb light more strongly in the ultraviolet region and are direct bandgap semiconductors, which can be potential photodetector materials. Rb3OI has a band gap value of 1.69eV, which has the potential to be used as the absorption layer material for perovskite solar cells. The results provide a theoretical basis for further experimental study of these three materials.