The metastable m-Ba2SnSe5 - Synthesis, Phase Transition, Crystal Structure, Structural Relations and Electronic Structure

A new modification of Ba2SnSe5 was synthesized in a flux reaction. The crystal structure of this compound was solved in the space group P12(1)/c1 with cell parameters of a = 21.17189(8) angstrom, b = 9.0915(3) angstrom, c = 24.7141(8) angstrom and beta = 125.621(1)degrees. The compound consists of two slightly different types of Sn4Se1412- as well as Se-3(2-) fragments and Ba2+ ions. The structure of the new modification is strongly related to the already reported alpha form, and therefore it is described using group-subgroup relations. To investigate the nature of this transition, thermal experiments and band structure calculations were performed.