Ab-initio Study of structural, elastic, electronic and optical properties of hexahalometallate single crystals K2XBr6(X = Se, Pt).

Some physical properties of hexahalometallate K₂XBr₆(X = Se, Pt) were computed in the zinc blend structure using GGA-PBESOL. The cell constant of K₂SeBr₆ and K₂PtBr₆ is consistent to the experiment value quoted in the literature, where the error is 0.95% and 1%. K₂SeBr₆ and K₂PtBr₆ present covalent bonding, high anisotropy and are ductile. The elastic constants of K₂SeBr₆ and K₂PtBr₆ are significantly smaller due to their larger reticular distances, lower Coulomb forces and then they are soft and damage tolerant. The interatomic separation is greater in K₂SeBr₆ than in K₂PtBr₆, hence the Coulomb interaction in K₂PtBr₆ is greater than that of K₂SeBr₆. The internal coordinate of Br atom in K₂PtBr₆ is lower than that of the same atom in K₂SeBr₆, and this can be explained by the fact that it is inversely proportional to the atom radius of Se and Pt. There are two major plasmonic processes, with intensities 3.7 and 1.35 located around 53.5 nm and 72.8 nm for K₂SeBr₆ and K₂PtBr₆. [ABSTRACT FROM AUTHOR]