Physics – Condensed Matter – Materials Science
Scientific paper
2009-11-14
Phys. Rev. B 80, 224102 (2009)
Physics
Condensed Matter
Materials Science
26 pages, 8 figures, 1 table; to appear in Phys. Rev. B 80 (2009)
Scientific paper
We present a first-principles study of native defects in NaAlH$_4$. Our analysis indicates that the structure and energetics of these defects can be interpreted in terms of elementary building blocks, which include $V_{\rm{AlH_4}}^+$, $V_{\rm{Na}}^-$, $V_{\rm{H}}^+$, H$_i^-$, and (H$_2$)$_i$. We also calculate migration barriers for several key defects, in order to compare enthalpies of diffusion to experimentally measured activation energies of desorption. From this, we estimate activation energies for diffusion of defects and defect pairs. We suggest that $V_{\rm{AlH_4}}^+$ and H$_i^-$, or $V_{\rm{Na}}^-$ and $V_{\rm{H}}^+$, may be responsible for diffusion necessary for desorption. We discuss the possible role of $V_{\rm{H}}^+$-H$_i^-$ complex formation. The values we find are in the range of activation energies reported for catalyzed desorption.
Hoang Khang
Janotti Anderson
Peles Amra
Van de Walle Chris G.
Wilson-Short Gareth B.
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