Malliga SuewattanaDavid J. SinghMahidol UniversityOak Ridge National Laboratory2018-09-242018-09-242010-07-28Physical Review B - Condensed Matter and Materials Physics. Vol.82, No.1 (2010)1550235X109801212-s2.0-77956540021https://repository.li.mahidol.ac.th/handle/20.500.14594/29303The local structure and dynamics of piezoelectric K1-x Na xNbO3 perovskite solid solutions with and without partial Ta substitution at x=0.5 are investigated using first principles calculations for supercells. The results are analyzed locally using the dynamical pair distribution functions. The local structures for Ta-substituted material show smaller off-centering of Ta compared to Nb. In addition, the dynamics of the relaxed structure indicate softer Nb force constants relative to Ta even though the Nb has shorter O nearest-neighbor distances than Ta. These results are discussed in relation to experimental measurements which show a decrease in Curie temperature and an increase in dielectric constant when Ta is partially substituted into K1-x NaxNbO3. © 2010 The American Physical Society.Mahidol UniversityMaterials SciencePhysics and AstronomyArticleSCOPUS10.1103/PhysRevB.82.014114