Ternary hypervalent silicon hydrides via lithium at high pressure

Hydrogen is rarely observed as a ligand in hypervalent species, however, we find that high-pressure hydrogenation may stabilize hypervalent hydrogen-rich materials. Focusing 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 different hypervalent anions: layered ${\mathrm{SiH}}_{5}{}^{\ensuremath{-}}$ and tricapped triangular prismatic ${\mathrm{SiH}}_{6}{}^{2\ensuremath{-}}$. These differ from octahedral ${\mathrm{SiH}}_{6}{}^{2\ensuremath{-}}$ described in earlier studies. In addition, there are further hydrogen-rich structures, ${\mathrm{Li}}_{3}{\mathrm{SiH}}_{10}$ and ${\mathrm{Li}}_{2}{\mathrm{SiH}}_{6+\ensuremath{\delta}}$, which may be stabilized at high pressure. Our work provides pointers to future investigations on hydrogen-rich materials.