First Principles Determination of Structural Properties fo NaNbO3

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

Bordeaux

Conferencia; 12th European Meeting on Ferroelectricity (EMF12).; 2011

In this work we report total energy calculations for different crystal structures of NaNbO3 over arange of unit cell volumes using the all-electron full-potential (L)APW method with two differentexchange-correlation functionals: the local-density approximation (LDA) and the Wu-Cohen generalizedgradient approximation (GGA-WC). We found that LDA not only produces the well knownunderestimation of the equilibrium volume of the system but it also predicts a wrong antiferroelectricground-state for the Sodium Niobate. In contrast, with the GGA-WC functional we obtain acell volume in great agreement whit the experiments and an improvement on the stability of theferroelectric phase relative to the antiferroelectric (figure 1). The small energy difference betweenthe two phases explains the coexisting ferroelectric and antiferroelectric structures observed in experiments.