Equation of state of 7 LiH and 7 LiD from x-ray diffraction to 94 GPa

Single-crystal synchrotron x-ray diffraction has been performed on solid ${}^{7}\mathrm{LiH}$ up to 36 GPa and solid ${}^{7}\mathrm{LiD}$ up to 94 GPa in helium as a hydrostatic medium. The rocksalt structure is stable up to the maximum pressure. An isotopic shift on the equation of state (EOS) is clearly measured and its magnitude falls in between various approximations of the contribution of the zero-point lattice vibrations. Finally, the EOS of LiH is compared to calculations and to the EOS of its isoelectronic solid, He.