Spin state of LaCoO3:: Dependence on CoO6 octahedra geometry -: art. no. 054420

The electronic structure of the rhombohedral LaCoO3 perovskite is calculated for a number of structures with varying CoO6 octahedra geometry. The calculations are based on the generalized gradient approximation (GGA) to the density functional theory and, in order to describe better the strong electron-electron correlation in Co 3d states, the GGA+U method is employed. Depending on the Co-O distance d and the Co-O-Co bond angle beta, the spin S of the cobalt ion is found to correspond either to the intermediate spin state [(IS), S=1] or to the low spin state [(LS), S=O]. The border line dividing the IS and LS states in the (d,p) space is determined. The IS state is more stable than the LS state for structures with longer Co-O distances and more open Co-O-Co angles. The GGA+U results are in agreement with recently observed pressure-induced IS-LS transition.