First-principles study of structural stabilities of AlH3 under high pressure

The structural stabilities and electronic properties of AlH3 under high pressure are investigated by using the plane-wave pseudopotential method. Our results demonstrate that the sequence of the pressure-induced phase transition is Fd3¯m(β)→cmcm(α′)→R3¯c(α)→Pnma(hp1)→Pm3¯n(hp2), and the transition pressures are 0.49, 0.91, 47, and 70 GPa, respectively. Im3¯m,Pnnm(γ) and P63/m structures are not stable in the 0-100 GPa. β, α′, α, and hp1 structures of AlH3 are nonmetals, while Pm3¯n structure of AlH3 is metallic, and the pressure-induced metallization is ascribed to phase transition under higher compression.