First-principles study of the optical properties of MgxTi1-xH2

Setten van, Michiel J. and Er, Süleyman and Brocks, Geert and Groot de, Robert A. and Wijs de, Gilles A. (2009) First-principles study of the optical properties of MgxTi1-xH2. Physical Review B: Condensed matter and materials physics, 79 (12). p. 125117. ISSN 1098-0121

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Abstract:	Thin films of MgxTi1-x show an optical black state upon hydrogenation. We calculate the dielectric function and the optical properties of MgxTi1-xH2, x=0.5, 0.75, and 0.875 using first-principles density-functional theory. We argue that the black state is an intrinsic property of these compounds, unlike similar optical phenomena observed in other metal hydride films. The structures of MgxTi1-xH2 are represented either by simple ordered or quasirandom structures. The density of states has a broad peak at the Fermi level, composed of Ti d states; hence, both interband and intraband transitions contribute to the optical response. Ordered structures have a plasma frequency of ~3 eV. The plasma frequency drops below 1 eV in disordered structures, which - as a result of interband transitions - then show a low reflection and considerable absorption in the energy range of 1-6 eV, i.e., a black state.
Item Type:	Article
Copyright:	© 2009 American Physical Society
Faculty:	Science and Technology (TNW)
Research Group:	Computational Materials Science (CMS)
Link to this item:	http://purl.utwente.nl/publications/61346
Official URL:	http://dx.doi.org/10.1103/PhysRevB.79.125117
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Metis ID: 257189