Vacancy-mediated dehydrogenation of sodium alanate

Vacancy-mediated dehydrogenation of sodium alanate.

Clarification of the mechanisms of hydrogen release and uptake in transition-metal-doped sodium alanate, NaAlH(4), a prototypical high-density complex hydride, has fundamental importance for the development of improved hydrogen-storage materials. In this and most other modern hydrogen-storage materials, H(2) release and uptake are accompanied by long-range diffusion of metal species. Using firs...

Towards understanding a mechanism for reversible hydrogen storage: theoretical study of transition metal catalysed dehydrogenation of sodium alanate.

On the basis of density functional theory and coupled-cluster CCSD(T) calculations we propose a mechanism of the dehydrogenation of transition metal doped sodium alanate. Insertion of two early 3d-transition metals, scandium and titanium, both of which are promising catalysts for reversible hydrogen storage in light metal hydrides, is compared. The mechanism is deduced from studies on the decom...

First-principles study of Ti-doped sodium alanate surfaces

We have performed first-principles calculations of thick slabs of Ti-doped sodium alanate sNaAlH4d, which allows one to study the system energetics as the dopant progresses from the surface to the bulk. Our calculations predict that Ti stays on the surface, substitutes for Na, and attracts a large number of H atoms to its vicinity. Molecular dynamics simulations suggest that the most likely pro...

Continuum theory of vacancy-mediated diffusion

We present and solve a continuum theory of vacancy-mediated diffusion (as evidenced, for example, in the vacancy driven motion of tracers in crystals). Results are obtained for all spatial dimensions, and reveal the strongly nongaussian nature of the tracer fluctuations. In integer dimensions, our results are in complete agreement with those from previous exact lattice calculations. We also ext...

Optical response of the sodium alanate system: GW0-BSE calculations and thin film measurements