Ab initio study of phase competition in (La1−c,Src)CoO3 solid solutions

(La1−c,Src)CoO3 (LSC) solid solutions are promising materials for high temperature electrochemical cells and cathodes of solid oxide fuel cells. The Density Functional Theory (DFT) was applied to calculate the energies of the different superstructures in LSC which are stable with respect to formation of anti-phase domains. The energy parameters determining the relative stability of the cubic superstructures (phases) are extracted from these calculations. Using the Concentration Wave formalism and the energy parameters for different phases from DFT calculations, the temperature dependences of the long-range order parameters were obtained characterizing the order–disorder transformations. ► Temperature of order-disorder phase transitions in (La,Sr)CoO3 depends on composition. ► The order-disorder transitions occur already around 400K. ► The composition with La 50% and Sr 50% reveals second-order phase transition.