Ag 4 SnGe 2 S 7 : A Noncentrosymmetric Chalcogenide in I 4 -II-IV 2 -VI 7 System with Non-Diamond-Like Structure Featuring 1D ∞ [SnGe 2 S 8 ] 6- Infinite Chain.

The I 4 -II-IV 2 -VI 7 metal chalcogenide system has become an attractive research system because of its excellent physical and chemical properties. Here, we report the discovery of a new Sn II -based quaternary chalcogenide in the I 4 -II-IV 2 -VI 7 system, Ag 4 SnGe 2 S 7 , with a non-diamond-like structure and crystallizing in the Cc space group. The compound is characterized by isolated pyramid-like [SnS 3 ] units and one-dimensional ∞ [SnGe 2 S 8 ] 6- infinite chains with two orientations formed by the corner-sharing connected [SnGe 2 S 8 ] 6- units. It has a band gap of 2.40 eV and is insensitive to air and moisture.