Electronic structure and exchange interactions in V15 magnetic molecules:: LDA+U results

Single-molecule magnets V-15 (K-6[V15As6O42(H2O)].8H(2)O) have attracted a great deal of attention recently. These magnets are promising systems for studying such fundamental problems as spin tunneling, spin coherence, and low-temperature spin relaxation. To understand in detail the internal magnetic and electronic structure, and the intramolecular interactions responsible for the formation and low-energy excitations in V-15 molecules, we have performed electronic structure calculations using the local spin density approximation with on-site repulsion paramter U (so-called LSDA+U) approach. The calculated values of magnetic moments and charge states of vanadium ions agree well with experiments confirming the V4+ state of vanadium ions. We found that for Usimilar to4-5 eV, good description of known properties of V-15 molecule can be achieved. Comparing the results of the band-structure calculations with the experiments, we have found that the LDA+U description of the V-15 magnet is in agreement with experimental data. (C) 2003 American Institute of Physics.