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Advances in Materials Science and Engineering
Volume 2017 (2017), Article ID 3981317, 13 pages
https://doi.org/10.1155/2017/3981317
Research Article

Consistent Atomic Geometries and Electronic Structure of Five Phases of Potassium Niobate from Density-Functional Theory

1Department Physik, Universität Paderborn, 33095 Paderborn, Germany
2Dipartimento di Fisica e Astronomia, Universitá di Padova, 35131 Padova, Italy

Correspondence should be addressed to Arno Schindlmayr; ed.nrobredap-inu@ryamldnihcs.onra

Received 8 September 2016; Revised 11 November 2016; Accepted 24 November 2016; Published 30 January 2017

Academic Editor: Pascal Roussel

Copyright © 2017 Falko Schmidt et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We perform a comprehensive theoretical study of the structural and electronic properties of potassium niobate () in the cubic, tetragonal, orthorhombic, monoclinic, and rhombohedral phase, based on density-functional theory. The influence of different parametrizations of the exchange-correlation functional on the investigated properties is analyzed in detail, and the results are compared to available experimental data. We argue that the PBEsol and AM05 generalized gradient approximations as well as the RTPSS meta-generalized gradient approximation yield consistently accurate structural data for both the external and internal degrees of freedom and are overall superior to the local-density approximation or other conventional generalized gradient approximations for the structural characterization of . Band-structure calculations using a HSE-type hybrid functional further indicate significant near degeneracies of band-edge states in all phases which are expected to be relevant for the optical response of the material.