BAND-STRUCTURE AND CLUSTER-MODEL CALCULATIONS OF LACOO(3) IN THE LOW-SPIN PHASE

We present band-structure and cluster-model calCulatiOns Of LaCoO3 in the low-spin phase. The purpose of these calculations is to contrast a nd complement the results and conclusions of recent spectroscopic stud ies. The total density of states (DOS) is compared to the photoemissio n spectrum; the agreement is very good except for the many-body satell ites which appear at higher binding energies. The unoccupied O p DOS r eproduces fairly well the O 1s x-ray-absorption spectrum; the main dis crepancy appears in the Co 3d region and is attributed to core-hole ef fects. The ground state predicted by the cluster-model calculation is highly covalent and contains mainly 62% of t2g6 (1A1) and 36% of t2g6e (g)(2E)L. The first (one-electron) removal state has more 3d6L than 3d 5 character whereas the first addition state is almost completely domi nated by the 3d7 state. This means that low-spin LaCoO3 is in the char ge-transfer regime and the optical band pp is of the p-d type. The Co 3d contribution to the photoemission spectrum calculated with the clus ter-model reproduces not only the leading peaks but also the many-body satellites. The main drawback in this case is the absence of the spec tral weight coming from the O 2p bands.