SrH22 as an analog to metal hydrogen in the 200 GPa range.

The bandgap closure of solid hydrogen into a molecular metal has recently been experimentally observed, but its detailed electronic and structural characterizations remain at the very edge of current high pressure physics capabilities. In 1983, N. Ashcroft suggested the possibility to use impurities to lower the hydrogen metallization transition pressure. The recent discovery of SrH22, the metal hydride with the highest hydrogen content discovered so far, offers to put in practice that prediction. The insulator to metal transition by bandgap closure in Sr-doped molecular hydrogen compound is expected to occur around 220 GPa.
This proposal aims at reproducing the synthesis of the SrH22 compound, to obtain it in pure form to be able to refine its structure, and to determine its pressure stability range and the structural changes upon entering the metal state. The structural study will be complemented by IR absorption measurements in our laboratory to measure the bandgap closure.