First-Principles Calculations of Structural Properties of NaNbO3

R. MACHADO; M. SEPLIARSKY; M. G. STACHIOTTI

FERROELECTRICS

TAYLOR & FRANCIS LTD

Lugar: Londres; Año: 2012 vol. 427 p. 98 - 104

0015-0193

We present ab-initio total energy calculations for different structures of NaNbO3 atdifferent volumes using two different exchange-correlation functionals: the Perdew andWang version of the local-density approximation (LDA) and the Wu and Cohen versionof the generalized gradient approximation (GGA-WC). We found that LDA not only underestimatesthe equilibrium volume of the system but also predicts an incorrect groundstate for this oxide. The GGA-WC functional, on the other hand, significantly improvesthe equilibrium volume and provides a relative phase stability in better agreement withexperiments. We then use the GGA to investigate the presence of structural instabilitiesas a function of volume in order to provide insights for the understanding of thestructural behavior of K1-xNaxNbO3 solid solutions.