For geometry optimizations and charge / spin density calculations, DFT was used as implemented within the CP2K package. In contrast to other transition metals, for V-based compounds, a computational treatment with both GGA and hybrid functionals yields excellent geometries and electronic structures. Therefore, all calculations were performed with the computationally more economic GGA, i.e. the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional, together with the valence double-ζ polarized (DZVP) basis set, and Goedecker-Teter-Hutter (GTH) pseudopotentials. Simulations were performed in the gas phase in a box of size 60×50×50 Å. SCF convergence parameter is 10 -5 .