Structure and hydrogen dynamics of pure and Ti-doped sodium alanate -: art. no. 060101

We have studied the structure, energetics, and dynamics of pure and Ti-doped sodium alanate (NaAlH4), focusing on the possibility of substitutional Ti doping in the bulk. Our ab initio calculations reproduce well the measured neutron inelastic scattering spectrum, which exhibits surprisingly strong and sharp two-phonon features. The calculations also reveal that substitutional Ti doping is energetically possible, and imply that Ti prefers to substitute for Na and is a powerful hydrogen attractor that facilitates multiple Al-H bond breaking. Our results hint at ways of improving the hydrogen dynamics and storage capacity of the alanates.