First principles modelling of magnesium titanium hydrides

Er, Süleyman and Setten van, Michiel J. and Wijs de, Gilles A. and Brocks, Geert (2010) First principles modelling of magnesium titanium hydrides. Journal of physics: Condensed matter, 22 (7). 074208. ISSN 0953-8984

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Abstract:	Mixing Mg with Ti leads to a hydride Mg(x)Ti(1-x)H2 with markedly improved (de)hydrogenation properties for x < 0.8, as compared to MgH2. Optically, thin films of Mg(x)Ti(1-x)H2 have a black appearance, which is remarkable for a hydride material. In this paper we study the structure and stability of Mg(x)Ti(1-x)H2, x= 0-1 by first-principles calculations at the level of density functional theory. We give evidence for a fluorite to rutile phase transition at a critical composition x(c)= 0.8-0.9, which correlates with the experimentally observed sharp decrease in (de)hydrogenation rates at this composition. The densities of states of Mg(x)Ti(1-x)H2 have a peak at the Fermi level, composed of Ti d states. Disorder in the positions of the Ti atoms easily destroys the metallic plasma, however, which suppresses the optical reflection. Interband transitions result in a featureless optical absorption over a large energy range, causing the black appearance of Mg(x)Ti(1-x)H2.
Item Type:	Article
Copyright:	© 2010 Institute of Physics
Faculty:	Science and Technology (TNW)
Research Group:	Computational Materials Science (CMS)
Link to this item:	http://purl.utwente.nl/publications/68605
Official URL:	http://dx.doi.org/10.1088/0953-8984/22/7/074208
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