Title: The location of Ti atom in sodium alanate: an ab initio spin-polarised study

Authors: A.J. Du, Sean C. Smith, G.Q. Lu

Addresses: Centre for Computational Molecular Science and ARC Centre for Functional Nanomaterial, The University of Queensland, AIBN Building 75, OLD 4072, Brisbane, Australia. ' Centre for Computational Molecular Science and ARC Centre for Functional Nanomaterial, The University of Queensland, AIBN Building 75, OLD 4072, Brisbane, Australia. ' Centre for Computational Molecular Science and ARC Centre for Functional Nanomaterial, The University of Queensland, AIBN Building 75, OLD 4072, Brisbane, Australia

Abstract: In this work, ab initio spin-polarised Density Functional Theory (DFT) calculations are performed to study the interaction of a Ti atom with a NaAlH₄(001) surface. We confirm that an interstitially located Ti atom in the NaAlH₄ subsurface is the most energetically favoured configuration as recently reported (Chem. Comm. (17) 2006, 1822). On the NaAlH₄(001) surface, the Ti atom is most stable when adsorbed between two sodium atoms with an AlH₄ unit beneath. A Ti atom on top of an Al atom is also found to be an important structure at low temperatures. The diffusion of Ti from the Al-top site to the Na-bridging site has a low activation barrier of 0.20 eV and may be activated at the experimental temperatures (∼323 K). The diffusion of a Ti atom into the energetically favoured subsurface interstitial site occurs via the Na-bridging surface site and is essentially barrierless.

Keywords: density functional theory; ab initio DFT calculation; spin polarisation; surface adsorption; diffusion; activation barrier; Ti atoms; titanium atoms; sodium alanate; nanotechnology; hydrogen storage systems.

DOI: 10.1504/IJNT.2007.014751

International Journal of Nanotechnology, 2007 Vol.4 No.5, pp.564 - 573

Published online: 06 Aug 2007 *

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