Ternary Hypervalent Silicon Hydrides via Lithium at High Pressure

Abstract: Hydrogen is rarely observed as ligand in hypervalent species, however, we find that high-pressure hydrogenation may stabilise hypervalent hydrogen-rich materials. Focussing on ternary silicon hydrides via lithium doping, we find anions composed of hypervalent silicon with H ligands formed under high pressure. Our results reveal two new hypervalent anions: layered-SiH${5}^{-}$ and tricapped trigonal prismatic SiH${6}^{2-}$. These differ from octahedral SiH${6}^{2-}$ described in earlier studies. In addition, there are further hydrogen-rich structures Li${3}$SiH${10}$ and Li${2}$SiH$_{6+\delta}$ which may be stabilised at high pressure. Our work provides pointers to future investigations on hydrogen-rich materials.