Synthesis of lithium polyhydrides above 130 GPa at 300 K

High hydrides with unusual stoichiometries have been predicted to become energetically favored in various hydrides of alkali and alkali earth metals under pressure. This paper reports on synchrotron infrared spectroscopic measurements on lithium hydride (LiH) compressed in a diamond anvil cell up to 215 GPa, showing that insulating lithium polyhydrides containing H₂ units are synthesized above 130 GPa at 300 K. The observed vibron frequencies are in good agreement with the predictions for LiH₂ and LiH₆.