Multi-phonon scattering and Ti-induced hydrogen dynamics in sodium   alanate
  We use ab initio methods and neutron inelastic scattering (NIS) to study the structure, energetics, and dynamics of pure and Ti-doped sodium alanate (NaAlH_4), focusing on the possibility of substitutional Ti doping. The NIS spectrum is found to exhibit surprisingly strong and sharp two-phonon features. The calculations reveal that substitutional Ti doping is energetically possible. Ti prefers to substitute for Na and is a powerful hydrogen attractor that facilitates multiple Al--H bond breaking. Our results hint at new ways of improving the hydrogen dynamics and storage capacity of the alanates. 
Jorge Iniguez (NIST and U. Maryland), T. Yildirim (NIST), T.J. Udovic   (NIST), E.H. Majzoub (SNL), M. Sulic (U. Hawaii), an...