DFT investigations of pressure effect on lead-free double perovskites Cs2ZrCl6 and Cs2ZrBr6: Structural stability and band gap evolution

Perovskites have piqued the interest of many people due to their exceptional properties and promising applications. In this paper, the effect of pressure on lead-free double perovskites Cs 2 ZrCl 6 is investigated using first-principles calculations. It demonstrates that Cs 2 ZrCl 6 is stable up to 75 GPa, and that the alternation of the charge density distribution on the conduction bands caused by external pressure can force Cs 2 ZrCl 6 to transform from an indirect band gap semiconductor to a direct band gap semiconductor, which is applicable for isostructural Cs 2 ZrBr 6 . This suggests that Cs 2 ZrCl 6 and Cs 2 ZrBr 6 have promising underlying applications in high-pressure environments. This work is also useful for designing novel perovskites with superior performance. • Pressure effect on double perovskites Cs 2 ZrX 6 (X=Cl, Br) were explored. • The structure of Cs 2 ZrX 6 can be stable up to ~75 GPa. • Pressure-induced indirect-direct band-gap transition was observed.