Effect of the <Emphasis Type="Italic">d</Emphasis> electrons on phase transitions in transition-metal sesquioxides |
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| Authors: | Koichiro Umemoto Renata M Wentzcovitch |
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| Institution: | (1) Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA;(2) Minnesota Supercomputing Institute and Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA;(3) Interactive Research Center of Science, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan |
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| Abstract: | We present a systematic density-functional study of phase relations in three 4d-transition-metal sesquioxides: Y2O3, Rh2O3, and In2O3. Y2O3 and In2O3 undergo pressure-induced transitions to phases with larger cation coordination number (from 6 to 7) at low pressures. However,
this does not occur in Rh2O3 at least up to ~300 GPa. This cannot be explained by usual arguments based on ionic-radii ratios often used successfully
to explain phase relations in simple-metal and rare-earth sesquioxides and sesquisulfides. Inspection of their electronic
structures shows that, in Rh2O3, the electronic occupancy of 4d orbitals, 4d
6, plays a fundamental role in the extraordinary stability of the Rh2O3(II)-type phase with respect to coordination increase. We point out that d-orbital occupancy is a fundamental factor in explaining phase relations in transition-metal sesquioxides and sesquisulfides. |
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