Huge-pressure-induced volume collapse in LiAlH4 and its implications to hydrogen storage

A detailed high-pressure study on LiAlH4 has been carried out using the ab initio projected augmented plane-wave method. Application of pressure transforms alpha- to beta-LiAlH4 (alpha-NaAlH4-type structure) at 2.6 GPa with a huge volume collapse of 17%. This abnormal behavior is associated with electronic transition from Al-s to -p states. At 33.8 GPa, a beta to gamma transition is predicted from alpha-NaAlH4-type to KGaH4-type structure. Up to 40 GPa LiAlH4 remains nonmetallic. The high weight percent of hydrogen, around 22% smaller equilibrium volume, and drastically different bonding behavior than alpha-phase indicate that beta-LiAlH4 is expected to be a potential hydrogen storage material.