Journal
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
Volume 250, Issue 10, Pages 2206-2214Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/pssb.201349186
Keywords
density functional theory; phase diagram; phase transitions; pressure; structure; titanium oxide
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Funding
- Graduate Education Innovation Program of Shanghai
- National Natural Science Foundation of China [51072213]
- Local Colleges Faculty Construction for Science and Technology Commission of Shanghai Municipality [11160501000]
- [13JC1402900]
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A systematic examination of structural phase transitions and mechanical properties for TiO2 under high pressure has been performed by using first-principles calculations. First, we show that the orthorhombic Pca21 structure becomes stabilize at certain pressure and temperature, whereas the cubic fluorite and pyrite structures are not energetically viable in the whole pressure range of 0-200GPa. These findings support that the experimentally assumed cubic TiO2 should be the Pca21-type TiO2. Secondly, our calculated equations of state for various TiO2 polymorphs are consistent with previous experimental and theoretical results. The only exception is the baddeleyite phase for which we find a significantly lower bulk modulus of 149GPa than the measured value 290-304GPa. Finally, our calculations reveal that the recently synthesized Fe2P-type TiO2 exhibits semiconducting features and has the potential to be a superhard material under ultrahigh pressure. It is shown that the high pressure could open a valid avenue for new hard or superhard materials. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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