Fyzikální ústav Akademie věd ČR

Seminar Monday, 09/05/2016 13:00 - 14:00

Speakers: Robert A. Evarestov (Head of Quantum Chemistry Department, Chemistry Institute of St. Petersburg State University, RUSSIA)
Place: seminar hall 117 FZU Slovanka
Presented in English
Organisers: Division of Optics

The results of the first-principle calculations [1] of electron and phonon properties of bulk SrTiO3 crystal demonstrate good agreement with the experimental data for the atomic and band structure, for the phonon frequencies and phase transition from cubic to tetragonal phase. Combining group-theoretical analysis and first-principles calculations the antiferrodistortive phase transition in ultrathin SrTiO3 (001) TiO2 -terminated films is confirmed and compared with a similar transition in the bulk [2]. The supercell model is used to calculate Gibbs free energy of oxygen vacancy formation [3]. It is shown that the oxygen vacancy induces the Jahn-Teller distortion and gives rise to triplet spin ground state.The application of the supercell model to Fe-doped SrTiO3 [4] enables a quantitative description of the experimentally found Jahn-Teller distortion in SrFexTi1-xO3. The combined use of ab initio quantum mechanical and x-ray absorption near edge structure (XANES) methods [5] confirms that the oxygen vacancies (VO) are located in the first coordination shell of Fe3+ ions in the cathodic region. The binding energy of such a complex is estimated as 0.4 eV. References 1. Robert A. Evarestov, Evgeny Blokhin, Denis Gryaznov, Eugene A. Kotomin and Joachim Maier, PHYSICAL REVIEW B 83, 134108 (2011) 2. Robert A. Evarestov, Evgeny Blokhin, Denis Gryaznov, Eugene A. Kotomin and Joachim Maier, PHYSICAL REVIEW B 88, 241407(R) (2013) 3. Denis Gryaznov, Evgeny Blokhin, Eugene A. Kotomin, Robert A. Evarestov, Annette Bussmann-Holder, and Joachim Maier, J. Phys. Chem. 117,13776(2013) 4. V. E. Alexandrov, J. Maier and R.A.Evarestov, PHYSICAL REVIEW B 77, 075111 (2008) 5. Evgeny Blokhin, Eugene Kotomin, Alexei Kuzmin, Juris Purans, Robert Evarestov and Joachim Maier, Applied Physics Letters, 102,112913 (2013)