Simulation studies of the phase stability of the Sr_n+1Ti _nO_3n+1 Ruddlesden-Popper phases

Atomistic simulation techniques are used to examine the stability of Ruddlesden-Popper (R-P) phases Sr_n+1Ti_nO_3n+1(n = 1, 2, 3, 4 and ∞). Various sets of empirical pair potentials are employed to determine the formation energies of the R-P phases. Formation energies are also calculated with Density Functional Theory (DFT). The tendency of a given R-P phase to dissociate into a lower order R-P phase plus SrTiO ₃ perovskite is found to increase with increasing n. The results obtained are compared with experiment and previous computational studies. The stability of intergrowth phases with respect to the pure R-P compounds is examined. In all cases the intergrowths are calculated to be thermodynamically less stable than the pure R-P phase, but the differences are in some cases negligible. Finally, the energy for SrO partial Schottky disorder in strontium titanate is computed taking the formation of R-P phases into account.