Influence of pressure on the different physical features of lead-free double perovskite materials K2SnX6 (X = Cl, and Br): DFT replication

Abstract

The influence of pressure (0–12 GPa) on several physical features of perovskite materials K₂SnX₆ (X = Cl, and Br) has been executed through DFT replication coded with CASTEP. Very close relation is noticed concerning the studied and synthesized lattice parameters. The studied compounds are mechanically stable under pressure according to Born's stability criteria. The Pugh's and Poisson's ratios indicate the brittle nature K₂SnCl₆ at 0 GPa and ductile nature at above 2 GPa. On the other hand, the phase K₂SnBr₆ exhibits ductile in nature at 0 GPa to high pressure. The increasing behaviors of machinable index with increasing pressure making these materials effectively useable in industrial applications. The determined Vickers hardness (H_v) values at several pressures of both the phases did not exceed 8 GPa which enables them to be more machinable and damage-tolerant. The decrease of band gap with increasing pressure ensures the probable application of these materials in optoelectronic devices. The bond length decreases with increasing pressure and consequently materials become harder. As the static dielectric constant of K₂SnBr₆ is higher than K₂SnCl₆, hence K₂SnBr₆ is more suitable for optoelectronic device applications. In the ultraviolet region, both the materials show their intense peak of absorption and conductivity. Both the studied compounds processes very low thermal conductivity in the entire pressure ranges comparing to the well-known thermal barrier coating (TBC) materials ABO₃ which confirming their better uses in industry as TBC materials. Having very high melting temperature at high pressure these compounds are suitable for high-temperature application purposes.