The magnesium-rich intermetallics Ir3.30(1)Mg17.96(4)In0.74(4) and Ir3Mg17.1(1)In1.9(1)

Phase analytical investigations in the system magnesium–iridium–indium revealed the magnesium-rich intermetallics Ir3.30(1)Mg17.96(4)In0.74(4) and Ir3Mg17.1(1)In1.9(1). The samples were prepared from the elements via induction melting in glassy carbon crucibles in a water-cooled sample chamber and subsequent annealing. Both intermetallics were investigated by X-ray powder and single-crystal diffraction: C2/c, image, image, image, image, image, image, 3076 F2 values, 108 variables for Ir3.30(1)Mg17.96(4)In0.74(4), and image, image, image, image, image, 3893 F2 values, and 115 variables for Ir3Mg17.1(1)In1.9(1). Both compounds show solid solutions. In Ir3.30(1)Mg17.96(4)In0.74(4), the indium site shows an occupancy by 69.9(4)% In+30.1(4)% Ir, and one magnesium site has a small mixed occupancy with indium, while nine atomic sites in Ir3Mg17.1(1)In1.9(1) show Mg/In mixing with indium occupancies between 1.2(3)% and 14.8(3)%. The relatively complex crystal structure is of a new type. It can be explained by a packing of coordination number 10 and 12 polyhedra around the iridium atoms. The crystal chemical peculiarities and chemical bonding in both intermetallics is briefly discussed.