Design and synthesis of Ba3SiSe5 with suitable birefringence modulated via MIV atoms in the Ba–MIV–Q (MIV = Si, Ge; Q = S, Se) system

Abstract

A new ternary Ba-based selenide, Ba₃SiSe₅, was synthesized by a high-temperature solid-state method. It crystallizes in the centrosymmetric space group Pnma (no. 62) of the orthorhombic system. The structure of the title compound consists of unique Se(4)Ba layers and discrete SiSe₄ tetrahedra. The structure and computational properties of Ba₃SiSe₅ are systematically studied together with those of the Ba–M^IV–Q (M^IV = Si, Ge; Q = S, Se) system, and show an interesting difference in dimensions formed by one of the crystallographic Ba atoms and M^IVQ₄ tetrahedra, as well as optical property transformations modulated by M^IV atoms. First principles methods were employed to obtain a better understanding of the relationship between structures and properties. Ba₃SiSe₅ maintains a moderate birefringence of 0.044@1064 nm and the real space atom cutting method indicates that the SiSe₄ tetrahedra make the major contribution to its birefringence.