Year: 2009
Type: article
Abstract: We present a first-principles study of native defects in ${\text{NaAlH}}_{4}$. Our analysis indicates that the structure and energetics of these defects can be interpreted in terms of elementary building blocks, which include ${V}_{{\text{AlH}}_{4}}^{+}$, ${V}_{\text{Na}}^{\ensuremath{-}}$, ${V}_{\text{H}}^{+}$, ${\text{H}}_{i}^{\ensuremath{-}}$, and ${({\text{H}}_{2})}_{i}$. 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 the diffusion of defects and defect pairs. We suggest that ${V}_{{\text{AlH}}_{4}}^{+}$ and ${\text{H}}_{i}^{\ensuremath{-}}$, or ${V}_{\text{Na}}^{\ensuremath{-}}$ and ${V}_{\text{H}}^{+}$, may be responsible for diffusion necessary for desorption. We discuss the possible role of ${V}_{\text{H}}^{+}{\text{-H}}_{i}^{\ensuremath{-}}$ complex formation. The values we find are in the range of activation energies reported for catalyzed desorption.
Source: Physical Review B
Institution: University of California, Santa Barbara
Language: Latvian
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1591149371