Hg[CS(NH 2 ) 2 ] 4 (SiF 6 ): a fluorosilicate crystal with large birefringence achieved via multi-functional group modification

(0.122@546 nm) and significantly surpasses most previously reported inorganic hexafluorosilicates. This work provides a viable method for improving the birefringence of hexafluorosilicate compounds.