Formation of NaCl-type monodeuteride LaD by the disproportionation reaction of LaD2

Previous x-ray diffraction measurements revealed the pressure-induced decomposition of an fcc ${\mathrm{LaH}}_{2.3}$ into H-rich and H-poor fcc phases around 11 GPa. The present neutron diffraction measurements on ${\mathrm{LaD}}_{2}$ confirm the formation of NaCl-type LaD as a counterpart of the D-rich ${\mathrm{LaD}}_{2+\ensuremath{\delta}}$ by disproportionation. First-principles enthalpy and lattice dynamic calculations demonstrate that the NaCl-type LaH is stabilized at high pressures and can be recovered at ambient conditions. Finding the NaCl-type LaH will pave the way for investigations on the site-dependent nature of hydrogen-metal interactions.