Abstract

Atomistic computer simulation techniques are used to investigate the surface properties and defect chemistry of the LaCoO₃ perovskite. The theoretical techniques are based upon efficient energy minimisation routines, a ‘two-region’ strategy and the Mott–Littleton methodology for the accurate modelling of surface and bulk defects. Sr and Ca dopants are calculated to be the most soluble of the alkaline earth metals, in accord with observation. Charge compensation is predicted to occur via oxygen ion vacancies which are believed to be key sites with regard to catalytic activity. Relaxed surface energies are calculated for the low index surfaces and the order of stability is found to be {110} > {100} > {111}. The equilibrium morphology of LaCoO₃ is predicted from the surface energies, in which the {110} surface is calculated to dominate in the absence of impurities or surface irregularities, with a lesser contribution from the {100} surface. The surface defect energies are generally lower than in the bulk crystal implying that the dopants and oxygen vacancies will segregate to the surfaces, thus enhancing their catalytic and electrochemical activity.