Layered GaGe₂Te: structure and chemical bonding

Abstract

The structure of the new compound GaGe2Te has been determined using nanofocused synchrotron radiation. The trigonal structure (space group P m1, a=4.0443(3) Å, c=14.923(2) Å, V=211.38(4) Å3; Z=2) consists of Ge bilayers sandwiched by Ga−Te layers. Ge and Ga are tetrahedrally coordinated. The layer packages are separated by a van der Waals gap with a Te−Te distance of 4.1502(7) Å. The structure resembles that of GaGeTe but features an additional Ge atom layer. Despite small scattering contrast of Ga and Ge, precise high‐resolution data enable unequivocal atom assignment as confirmed by R values of different models. DFT calculations suggest only a small extent of charge transfer, which is confirmed by both Bader and Mulliken charges. Thus, bonding within the layer packages is predominantly covalent, especially between Ga and Ge. Formal oxidation states according to GaIIIGe(0)Ge−ITe−II, i. e. assuming rather ionic Ge−Ga bonds, convey a much less realistic situation than GaIIGe2(0)Te−II, which is in line with GaGeTe.