ORBITAL AND SPILL ORDERINGS IN YVO3 AND LAVO3 IN THE GENERALIZED GRADIENT APPROXIMATION

The orbital and spin orderings of d(2) Jahn-Teller systems are studied in the generalized gradient approximation (GGA) by using the full-pot ential linearized augmented-plane-wave method. For the low temperature distorted crystal structures in YVO3 and LaVO3 perovskites, we show t hat orbital orderings and insulating band structures are obtained prop erly in GGA, but are not in the local spin density approximation. Bond length alternation in the ab plane cause the C-type and G-type orderi ngs of d(yz) and d(zx) orbitals, which in turn stabilize theG-type and C-type antiferromagnetic spin orderings in YVO3 and LaVO3, respective ly. The total energy calculation partially confirms the relation betwe en orbital and spin orderings, and indicates that the extent of the or bital ordering is still insufficient for YVO3 in GGA.