Stabilization and electronic topological transition of hydrogen-rich metal LiMoH under high pressures from first-principles predictions.

Regarded as doped binary hydrides, ternary hydrides have recently become the subject of investigation since they are deemed to be metallic under pressure and possibly potentially high-temperature superconductors. Herein, the candidate structure of LiMoH is predicted by exploiting the evolutionary searching. Its high-pressure phase adopts a hexagonal structure with P6/mcm space group. We used first-principles calculations including the zero-point energy to investigate the structures up to 200 GPa and found that the P6cm structure transforms into the P6/mcm structure at 48 GPa. Phonon calculations confirm that the P6/mcm structure is dynamically stable. Its stability is mainly attributed to the isostructural second-order phase transition. Our calculations reveal the electronic topological transition displaying an isostructural second-order phase transition at 160 GPa as well as the topology of its Fermi surfaces. We used the projected crystal orbital Hamilton population (pCOHP) to examine the nature of the chemical bonding and demonstrated that the results obtained from the pCOHP calculation are associated with the electronic band structure and electronic localized function.