SrMg2Ga2 with ThCr2Si2-type structure

Abstract The gallide SrMg2Ga2 was obtained by direct reaction of the elements in a sealed tantalum ampoule. Single crystals were grown by slowly cooling the sample within a muffle furnace. The SrMg2Ga2 structure was refined from single crystal X-ray diffractometer data: I4/mmm, a = 450.52(7), c = 1169.39(18) pm, wR2 = 0.0349, 164 F2 values, 11 variables. The magnesium and gallium atoms build up a three-dimensional [Mg2Ga2] network which is composed of layers of edge-sharing MgGa4 tetrahedra with 280 pm Mg–Ga. Adjacent layers are condensed by Ga–Ga bonding (253 pm). The strontium atoms fill large Ga8Mg8 cages. Electronic structure calculations within Density Functional Theory (DFT) show charge transfers from Sr and Mg to Ga with ionocovalent behavior. The electronic density of states is dominated by Ga states and reveals metallic behavior. The chemical bonding is strong with dominant Mg–Ga and Ga–Ga mixing.