Influence of wave-function updates in GW calculations on titanates

Gijae Kang, Youngho Kang, and Seungwu Han
Phys. Rev. B 91, 155141 – Published 23 April 2015

Abstract

We investigate quasiparticle band structures of rutile and anatase phases of TiO2 and cubic SrTiO3 using various levels of GW approximations such as G0W0, GW0, GW, QPGW0, and QPGW. It is found that the quasiparticle band gap increases as the self-consistency level is ratcheted up from G0W0 to GW0 and GW, and the GW results overestimate the band gap by 50% in comparison with the experimental values. Interestingly, when the wave functions are updated in QPGW0 and QPGW, the band gap is significantly reduced, which is opposite to the tendency known for other materials. The experimental band gap is most closely reproduced by QPGW0 within 10% error. We explain the improvement by the wave-function update in terms of the local change in the charge density, which is different at Ti and O sites and reduces the quasiparticle energy gap.

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  • Received 3 September 2014
  • Revised 27 February 2015

DOI:https://doi.org/10.1103/PhysRevB.91.155141

©2015 American Physical Society

Authors & Affiliations

Gijae Kang, Youngho Kang, and Seungwu Han*

  • Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 151-755, Korea

  • *hansw@snu.ac.kr

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Vol. 91, Iss. 15 — 15 April 2015

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