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

Autor:	Miguel Moreno, J. A. Aramburu, Pablo García-Fernández
Rok vydání:	2015
Předmět:	Condensed Matter::Materials Science Lattice constant Ionic radius Condensed matter physics Chemistry Impurity General Physics and Astronomy Density functional theory Electronic structure Physical and Theoretical Chemistry Ferroelectricity Instability Ion
Zdroj:	Chemical Physics. 460:83-89
ISSN:	0301-0104
DOI:	10.1016/j.chemphys.2015.05.018
Popis:	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 Ni 2+ impurity can happen in SrO, in agreement with experimental data, while not for smaller Cr 3+ or Ti 4+ 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 Mn 2+ in SrO. Our results indicate that an off-centre motion in MgO:Ni 2+ is rather unlikely and that the local contributions to the instability in pure BaTiO 3 are not enough to induce ferroelectricity if just the movement of Ti 4+ ion is considered.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::4ff632868e43e3d2acc9b58f16443d58 https://doi.org/10.1016/j.chemphys.2015.05.018 Zobrazit plný text záznamu Full Text from ScienceDirect