Insulating fcc YH3-δ stabilized by MgH2


Molen, S.J. van der and Nagengast, D.G. and Gogh, A.T.M. van and Kalkman, J. and Kooij, E.S. and Rector, J.H. and Griessen, R. (2001) Insulating fcc YH3-δ stabilized by MgH2. Physical Review B: Condensed matter and materials physics, 63 (23). p. 235116. ISSN 1098-0121

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Abstract:We study the structural, optical, and electrical properties of MgzY1-z switchable mirrors upon hydrogenation. It is found that the alloys disproportionate into essentially pure YH3-δ and MgH2 with the crystal structure of YH3-δ dependent on the Mg concentration z. For 0<z<0.1, both hcp and fcc YH3-δ are observed, whereas for z>~0.1 only cubic YH3-δ is present. Interestingly, cubic YH3-δ is expanded compared to YH2, in disagreement with theoretical predictions. From optical and electrical measurements we conclude that cubic YH3-δ is a transparent insulator with properties similar to hexagonal YH3-δ. Our results are inconsistent with calculations predicting fcc YH3-δ to be metallic, but they are in good agreement with recent GW calculations on both hcp and fcc YH3. Finally, we find an increase in the effective band gap of the hydrided MgzY1-z alloys with increasing z. Possibly this is due to quantum confinement effects in the small YH3 clusters.

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Copyright:© 2001 The American Physical Society
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Metis ID: 202523