New Ternary Silicide LiRh₂Si₂ – Structure and Bonding Peculiarities

Abstract

Abstract The silicide LiRh 2 Si 2 was synthesized from the elements in a sealed niobium ampoule and was characterized by X‐ray powder and single‐crystal diffraction: FeMo 2 B 2 type (ordered version of U 3 Si 2 ), P 4/ mbm , a = 698.1(5), c = 274.6(4) pm, wR 2 = 0.0842, 186 F 2 values and 11 variables. The rhodium and silicon atoms build up a covalently bonded three‐dimensional [Rh 2 Si 2 ] network (244–248 pm Rh–Si), in which the lithium atoms fill larger channels which extend along the c axis. A similar structural arrangement occurs in LiY 2 Si 2 , however, the strong difference in size between rhodium and yttrium leads to different distortions. LiRh 2 Si 2 and LiY 2 Si 2 are isopointal rather than isotypic. The crystal chemistry and bonding peculiarities of both silicides are discussed on the basis of ab initio electronic structure calculations. 7 Li solid‐state NMR studies on LiRh 2 Si 2 revealed restricted motional narrowing due to lithium atomic diffusion in the temperature range 170–450 K.