Ternary arsenides ATt3As3 (A=K, Rb; Tt=Ge, Sn) with layered structures

•ATt3As3 (A=K, Rb; Tt=Ge, Sn) contains Tt atoms in three oxidation states.•The structure differs from NaGe3P3 in terms of layer stacking arrangement.•The compounds are predicted to be narrow band gap semiconductors.

The four ternary arsenides ATt3As3 (A=K, Rb; Tt=Ge, Sn) were obtained by reaction of the elements at 600–650 °C. They adopt an orthorhombic structure (space group Pnma, Z=4, with cell parameters ranging from a=9.9931(11) Å, b=3.7664(4) Å, c=18.607(2) Å for KGe3As3 to a=10.3211(11) Å, b=4.0917(4) Å, c=19.570(2) Å for RbSn3As3) containing corrugated [Tt3As3] layers built from Tt-centred trigonal pyramids and tetrahedra forming five-membered rings decorated with As handles. They can be considered to be Zintl phases with Tt atoms in +4, +3, and +1 oxidation states. Band structure calculations predict that these compounds are semiconductors with narrow band gaps (0.71 eV in KGe3As3, 0.50 eV in KSn3As3).

Graphical abstractTernary arsenides ATt3As3 (A=K, Rb; Tt=Ge, Sn) contain corrugated layers with Tt atoms in three different oxidation states and are narrow band gap semiconductors.Figure optionsDownload full-size imageDownload as PowerPoint slide