Dresden 2003 – wissenschaftliches Programm
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M: Metallphysik
M 41: Postersitzung
M 41.38: Poster
Donnerstag, 27. März 2003, 14:30–16:30, HSZ
Defects at the Σ3(111) boundary in strontium titanate — •Sibylle Gemming1 and Michael Schreiber1,2 — 1Institut für Physik, Technische Universität, D-09107 Chemnitz — 2School of Engineering and Science, International University Bremen, D-28725 Bremen
The influence of defects on the atom arrangement and on the electronic structure of the Σ3(111) grain boundary in strontium titanate has been investigated by density functional modelling with the plane-wave pseudopotential band-structure code ABINIT [1]. The undisturbed Σ3(111)[110] symmetrical twin boundary is a low-energy, bulk-like defect with an elongated Ti-Ti-distance across the interface compared with the coincidence site lattice model [2]. In the present calculations oxygen vacancies and metal impurities are introduced in the grain boundary plane and in its close vicinity. The resulting supercells model the change of the formal Ti oxidation state from 4+ to 3+ and its consequences on the geometric and electronic structure of the boundary. Both vacancies and impurities reduce the Coulomb repulsion of the Ti columns across the interface. This leads to a contracted Ti-Ti distance as well as a reduced excess volume at the boundary. Thus, the coincidence site lattice model provides building blocks which are already quite close to the ones of the optimised structure. In the high dopant limit which is investigated in the present study, there exists a thermodynamic driving force for vacancies and impurities to segregate to the grain boundary. [1] URI http://www.abinit.org [2] S. Hutt, S. Köstlmeier, C. Elsässer, J. Phys. Condens. Matter 13 (2001) 3949.