New ternary silicide LiRh₂Si₂ - structure and bonding peculiarities

Tim Dinges (1) , Ute Ch. Rodewald (1) , Samir F. Matar (2) , Helmut Eckert (3) , Rainer Pöttgen (1)

1 Institut für Anorganische und Analytische Chemie
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
3 Institut für Physikalische Chemie

The silicide LiRh₂Si₂ was synthesized from the elements in a sealed niobium ampoule and was characterized by X-ray powder and single-crystal diffraction: FeMo₂B₂ type (ordered version of U₃Si₂), P4/mbm, a = 698.1(5), c = 274.6(4) pm, wR2 = 0.0842, 186 F² values and 11 variables. The rhodium and silicon atoms build up a covalently bonded three-dimensional [Rh₂Si₂] 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 LiY₂Si₂, however, the strong difference in size between rhodium and yttrium leads to different distortions. LiRh₂Si₂ and LiY₂Si₂ 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. ⁷Li solid-state NMR studies on LiRh₂Si₂ revealed restricted motional narrowing due to lithium atomic diffusion in the temperature range 170-450 K.

Mots clés: Lithium compounds; Crystal chemistry; Chemical bonding; Density functional calculations; Solid State NMR spectroscopy

Domaines: Matériaux

Tim Dinges, Ute Ch. Rodewald, Samir F. Matar, Helmut Eckert, Rainer Pöttgen. New ternary silicide LiRh₂Si₂ - structure and bonding peculiarities. Journal of Inorganic and General Chemistry / Zeitschrift für anorganische und allgemeine Chemie, 2009, 635 (12), pp.1894-1903. ⟨10.1002/zaac.200900102⟩. ⟨hal-00435827⟩