A detailed high-pressure study on ${\mathrm{LiAlH}}_4$ has been carried out using the ab initio projected augmented plane-wave method. Application of pressure transforms $\alpha -$ to $\beta -{\mathrm{LiAlH}}_4$ $(\alpha -{\mathrm{NaAlH}}_4$-type structure) at 2.6 GPa with a huge volume collapse of 17%. This abnormal behavior is associated with electronic transition from $\mathrm{Al}-s$ to -$p$ states. At 33.8 GPa, a $\beta$ to $\gamma$ transition is predicted from $\alpha -{\mathrm{NaAlH}}_4$-type to ${\mathrm{KGaH}}_4$-type structure. Up to 40 GPa ${\mathrm{LiAlH}}_4$ remains nonmetallic. The high weight percent of hydrogen, around 22% smaller equilibrium volume, and drastically different bonding behavior than $\alpha$-phase indicate that $\beta -{\mathrm{LiAlH}}_4$ is expected to be a potential hydrogen storage material.

• Received 27 August 2003

DOI:https://doi.org/10.1103/PhysRevB.68.212101