First principles modelling of magnesium titanium hydrides - Condensed Matter > Materials ScienceReport as inadecuate




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Abstract: Mixing Mg with Ti leads to a hydride MgxTi1-xH2 with markedly improveddehydrogenation properties for x < 0.8, as compared to MgH2. Optically, thinfilms of MgxTi1-xH2 have a black appearance, which is remarkable for ahydride material. In this paper we study the structure and stability ofMgxTi1-xH2, x= 0-1 by first-principles calculations at the level of densityfunctional theory. We give evidence for a fluorite to rutile phase transitionat a critical composition xc= 0.8-0.9, which correlates with theexperimentally observed sharp decrease in dehydrogenation rates at thiscomposition. The densities of states of MgxTi1-xH2 have a peak at the Fermilevel, composed of Ti d states. Disorder in the positions of the Ti atomseasily destroys the metallic plasma, however, which suppresses the opticalreflection. Interband transitions result in a featureless optical absorptionover a large energy range, causing the black appearance of MgxTi1-xH2.



Author: S├╝leyman Er, Michiel J. van Setten, Gilles A. de Wijs, Geert Brocks

Source: https://arxiv.org/







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