Off-centre motion in doped cubic oxides: A general view on the instability

Abstract: The existence of an off-centre distortion for impurities in cubic oxides is explored by Density Functional Theory calculations. We find that models based on ionic radii are inadequate to explain the off-centre instability. By contrast, increase of the nominal impurity charge or decrease of the host lattice constant act against the off-centre distortion. This explains why the motion of just the Ni2+ impurity can happen in SrO, in agreement with experimental data, while not for smaller Cr3+ or Ti4+ ions in the same lattice. Moreover, the different electronic structure and coupling to the host lattice are shown to be behind a small but positive force constant for Na+ and Mn2+ in SrO. Our results indicate that an off-centre motion in MgO:Ni2+ is rather unlikely and that the local contributions to the instability in pure BaTiO3 are not enough to induce ferroelectricity if just the movement of Ti4+ ion is considered.

 Fuente: Chemical Physics 460 (2015) 83–89

Editorial: Elsevier

 Fecha de publicación: 01/10/2015

Nº de páginas: 7

Tipo de publicación: Artículo de Revista

DOI: 10.1016/j.chemphys.2015.05.018

ISSN: 0301-0104,1873-4421

Proyecto español: FIS2012-30996 ; FIS2012-37549-C05-4

Url de la publicación: https://doi.org/10.1016/j.chemphys.2015.05.018