Relative stability of low-index V2O5 surfaces: a density functional investigation

Ab initio density functional calculations of the structural and electronic properties of V2O5 bulk and its low-index surfaces are presented. For the bulk oxide and the (010) surface (the natural cleavage plane) a good agreement with experiment and with earlier ab initio calculations is found. For the first time, the investigations are extended to other low-index surfaces: (001) and (100). On both surfaces, termination conserving a bulk-like stoichiometry is preferred, but—in contrast to the (010) surface—a strong structural relaxation takes place. Relaxation reduces the surface energy from 1.16 to 0.48 J m−2 for the (001) and from 0.61 to 0.55 J m−2 for the (100) surface. Although the relaxed surface energies are still one order of magnitude higher than calculated for the (010) surface (0.047 J m−2), the Wulff construction demonstrates that (001) and (100) surfaces contribute about 15% of the total surface area of a V2O5 crystallite, indicating a non-negligible role in the catalytic activity of V2O5.