Large-scale computer modeling of ABO3 perovskite surfaces and defects therein

• Applicant: Dr. Roberts I. Eglitis
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2007 to 2008
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 35020279

• Final Report Year: 2009

Final Report Abstract

We present the results of calculations of surface relaxations, energetics and bonding properties for BaTiO3, PbTiO3, SrTiO3 and CaTiO3 (001) and (011) surfaces using a hybrid description of exchange and correlation. We consider both AO (A = Ba, Pb, Ti or Ca) and TiO2 terminations of the nonpolar (001) surface and A, TiO and O terminations of the polar (011) surface. On the (001) surfaces, we find that all upper-layer atoms relax inwards, while outward relaxations of all atoms in the second layer are found at both kinds of (001) terminations and for all four materials. The only exceptions there are O atoms on SrO-terminated SrTiO3 (001) surface upper layer and TiO2-terminated PbTiO3 (001) surface upper layer, which relax upwards. The surface energies for AO and TiO2-terminated BaTiO3, PbTiO3, SrTiO3 and CaTiO3 (001) surfaces are quite similar. The smallest calculated surface energy between all (001) surfaces is for TiO2-terminated PbTiO3 (001) surface (0.74 eV), while the largest surface energy is for TiO2-terminated SrTiO3 (001) surface (1.23 eV). In contrast to (001) surfaces, different terminations of the (011) surface lead to very different surface energies. For example in the case of CaTiO3 (011) surfaces they are 1.86 eV, 1.91 eV and 3.13 eV for the O-terminated, Ca-terminated and TiO-terminated (011) surface, respectively. Our results for CaTiO3 surface energies contrast sharply with those of Zhang et al. 2007, where the authors found a rather different pattern of surface energies. We predict a considerable increase in the Ti-O chemical bond covalency near the BaTiO3, PbTiO3, SrTiO3 and CaTiO3 (011) surfaces as compared both to the bulk and to the (001) surface.

Publications

• Ab initio calculations of BaTiO3 and PbTiO3 (001) and (011) surface structures, Phys. Rev. B 76, 155439 (2007)
  R. I. Eglitis and D. Vanderbilt
  
• Ab initio calculations of BaTiO3, PbTiO3 and SrTiO3 (001) and (011) surface structures, Fundamental Physics of Ferroelectrics 2008, Colonial Williamsburg, VA, February 10-13, 2008, pages 70-71
  R. I. Eglitis and D. Vanderbilt
  
• Ab initio calculations of BaTiO3, PbTiO3 and SrTiO3 (001) and (011) surfaces, American Physical Society March Meeting, New Orleans, March 10-14, 2008, page 347
  R. I. Eglitis and D. Vanderbilt
  
• Ab initio calculations of the atomic and electronic structure of CaTiO3 (001) and (011) surfaces, Phys. Rev. B 78, 155420 (2008)
  R. I. Eglitis and D. Vanderbilt
  
• First-principles calculations of atomic and electronic structure of SrTiO3 (001) and (011) surfaces, Phys. Rev. B 77, 195408 (2008)
  R. I. Eglitis and D. Vanderbilt