Vanadium oxide compounds with quantum Monte Carlo

Calculations with the diffusion quantum Monte Carlo method are presented for vanadium oxide molecules VOn0/+ with n = 1-4 and for V2O5. Atomization and ionization energies are calculated as well as oxygen abstraction energies. The fixed-node approximation is compared for guide functions with orbitals from B3LYP and BP86 calculations and higher accuracy was obtained with the latter orbitals. Additionally, all-electron and pseudopotential calculations are compared for the oxygen atom. The overall accuracy is found to be comparable to CCSD(T) calculations where experimental data is available.