SrMg2Ga2 with ThCr2Si2-type structure.

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. [ABSTRACT FROM AUTHOR]