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).

Ternary 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 as PowerPoint slide