Structural Stability of Complex Hydrides:LiBH4Revisited

Abstract

A systematic approach to study the phase stability of ${\mathrm{L}\mathrm{i}\mathrm{B}\mathrm{H}}_4$ based on ab initio calculations is presented. Three thermodynamically stable phases are identified and a new phase of $Cc$ symmetry is proposed for the first time for a complex hydride. The x-ray diffraction pattern and vibrational spectra of the $Cc$ structure agree well with recently reported experimental data on ${\mathrm{L}\mathrm{i}\mathrm{B}\mathrm{H}}_4$. Calculations of the free energy at finite temperatures suggest that the experimentally proposed $P{6}_{3}mc$ phase is unstable at $T>0\mathrm{K}$.