Variational study of the antiferromagnetic insulating phase of V2 O3 based on Nth order muffin-tin-orbitals

Motivated by recent results of Nth order muffin-tin-orbital (NMTO) implementation of density-functional theory, we re-examine low-temperature ground-state properties of the antiferromagnetic insulating phase of vanadium sesquioxide V2 O3. In fact, the hopping matrix elements within the nearest-neighbor vanadium pair, obtained by the NMTO-downfolding procedure, are strongly reduced compared to those previously obtained using the downfolding procedure of Castellani [Phys. Rev. B18, 4945 (1978); 18, 4967 (1978);18, 5001 (1978)]. This could imply a breakdown of the molecular picture. We use the NMTO hopping matrix elements as input and perform a variational study of the ground state. We find that the formation of stable molecules throughout the crystal is not favorable in this case, though the experimentally observed magnetic structure can still be obtained in the atomic variational regime. However, the resulting ground state (two t2g electrons occupying the degenerate eg doublet) is in contrast with many well-established experimental observations. We discuss the implications of this finding in the light of the importance of nonlocal electronic correlations in V2 O3.