Search of B1 to B2 transition in LiH above 300 GPa.

This proposal aims to extend previous measurements beyond 250 GPa, reaching up to 400 GPa. Our experimental strategy leverages the discovery of lithium reactivity-diffusion in diamond anvil and capitalizes on the reconstructed ID27 beamline. Two paths will be followed. On one hand, we will perform second-time scale XRD diffraction during few minute-time scale rapid compression ramp on pure LiH. On the other hand, we will load a µm size single crystal LiH in Ne pressure transmitting medium and will perform single crystal X-ray diffraction in a toroidal DAC to extend accurately the determination of the EoS of LiH in the 400 GPa range. A significant output would be the observation of the B1-B2 transition.