Crystal and electronic structures of a new hexagonal silicide Sc38Co144Si97

Sc38Co144Si97 was prepared from the elements by arc melting under argon and subsequent annealing at 800 ​°C for 350 ​h. Single-crystal X-ray diffraction reveals Sc38Co144Si97 to crystallize in a new hexagonal structure type: Pearson's symbol hP279, space group P63/m, a ​= ​33.624(7), c ​= ​3.639(1) Å. The crystal structure of Sc38Co144Si97 can be considered as a 2D intergrowth of three kinds of fragments of simpler structure types: hexagons and quadrilaterals with the arrangements of the Sc6Co30Si19-type and triangles with the arrangement of the Gd4Co13(Si, P)9-type. Quantum chemical calculations have been performed to analyze the electronic structure and provide deeper insight into the structure-property relationships. The Extended Hückel (EH) calculation indicates that Co in Sc38Co144Si97 adopts close to a d10 configuration owing to the covalent interaction with Si. The Sc–Co and Sc–Si interactions are more ionic, and Co–Co and Co–Si bonds are more covalent interactions.