First-principles investigations of the pressure-induced structural transitions in Mg(AlH ₄ ) ₂

A systematic investigation is presented of the high-pressure structural stability of Mg(AlH(4))(2) using a plane-wave pseudo-potential method. The total-energy calculations show that under ambient pressure the structure of α-Mg(AlH(4))(2) found by experiments is more stable than the other proposed structures, and with pressure increasing the α to β (δ-Zr(MoO(4))(2)-type structure) and β to γ (Ca(BF(4))(2)-type structure) transitions occur at 0.67 and 10.28 GPa respectively, accompanied with volume reductions of 6.6% and 8.7%. A detailed study of the electronic structures reveals the bonding characteristics between Al and H and between Mg and H as well as the nonmetallic features of α, β, and γ phases under pressure of up to 20.0 GPa. Their electronic structures are mainly responsible for the relative high-pressure stability of the three phases. Finally, an analysis of their structural relations indicates that it is possible to produce the [Formula: see text] structural transition by applying pressure.