Synthesis, crystal and electronic structure, and optical property of the pentanary chalcohalide Ba3KSb4S9Cl

Abstract

The pentanary chalcohalide Ba3KSb4S9Cl has been prepared from stoichiometric mixtures of KCl, Ba, Sb, and S in an evacuated silica tube, which is the first example of chalcohalides in the pentanary A/Ae/Sb/Q/X (A=alkali metal; Ae=alkaline-earth metal; Q=S, Se, Te; X=F, Cl, Br, I) system. This material crystallize in the Pnnm space group and its new structure type comprises one-dimensional (1D) [Sb3S7]5− chains running down the [001] direction separated by isolated dimeric Sb2S4 polyhedra, Ba2+, K+, and Cl−, respectively. The optical gap of 1.99eV for Ba3KSb4S9Cl was deduced from the UV/vis reflectance spectroscopy and DFT study indicates a indirect band gap with an electronic transfer excitation of S 3p to Sb 5p orbital electrons.