Modelling of the phase transitions sequence in KNbO 3 and BaTiO 3

S. TINTE; M. SEPLIARSKY; R. L. MIGONI; C. O. RODRIGUEZ

Z. PHYS. - B - COM. MAT.

Sringer-Verlag

Año: 1997 vol. 104 p. 721 - 724

0722-3277

Interatomic potentials are determined in the frame-work of the nonlinear oxygen polarizability model to de-scribe the structural behavior of KNbO 3 and BaTiO 3 as afunction of temperature. To this purpose, the adiabatic po-tential is evaluated for different ferroelectric distortions andthe model potential parameters are improved by compar-ing with total energies from full-potential LMTO calcula-tions. Phonon dispersion curves are computed to test if themodel reproduces the pronounced two-dimensional characterinstabilities found by first-principles lattice dynamics usinga linear response approach. Finally, the phase diagram forKNbO 3 is obtained through a constant-pressure moleculardynamics simulation.