Synthesis, crystal structure and optical properties of K2Cu2GeS4

A new compound K2Cu2GeS4 was successfully synthesized by using molten thiourea reactive flux method. The structure was determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic system of space group P2/c with a unit cell of a = 7.063 (3) angstrom, b = 5.435 (3) angstrom, c = 11.037 (6) angstrom and beta - 112.83 (3)degrees. The crystal structure of K2Cu2GeS4 is composed of defective anti-PbO like [Cu2GeS4](2) layers which are interleaved by K-1 cations. This compound is a semiconductor with an indirect band gap of 2.3 (1) eV, which is derived from optical absorption spectrum. First principles calculations reveal that K(2)Cu(2)GeS4 has interesting intermediate bands consisting of Ge-4s and S-3p orbitals. This new semiconductor is potentially suitable for solar photocatalytic and photoelectric applications. (C) 2017 Elsevier B.V. All rights reserved.