Computer simulations of thermal expansion in lanthanum-based perovskites

Differential thermal expansion is important when two strongly bonded cerami cs are subjected to high temperatures, as in solid oxide fuel cells. Free e nergy minimization (EM) and molecular dynamics (MD) techniques were used to simulate the thermal expansion of the perovskites (La,Ca)CrO3 and (La,Sr) (Co, Fe)O-3 on the atomistic scale. This paper explores the use of empirica l partial charge interatomic potentials to represent the partially covalent bonding in these materials. The EM simulations underpredicted the thermal expansion coefficients (CTEs) by up to 26% due to limitations in the potent ials. The MD simulations predicted the CTEs to within 17% of experimental d ata for (La,Ca)CrO3. MD predictions of the CTEs for (La,Sr)(Co,Fe)O-3 were significantly lower than the experimental data due to the approximate natur e of the Co(4+)and Fe4+ interatomic potentials. Improvements in these resul ts are possible if more extensive databases become available for refining t he potentials and effective charges. (C) 2001 Academic Press.