Van der Waals Interactions in DFT using Wannier Functions: improved $C_6$ and $C_3$ coefficients by a new approach

A new implementation is proposed for including van der Waals interactions in Density Functional Theory using the Maximally-Localized Wannier functions. With respect to the previous DFT/vdW-WF method, the present DFT/vdW-WF2 approach, which is based on the simpler London expression and takes into account the intrafragment overlap of the localized Wannier functions, leads to a considerable improvement in the evaluation of the $C_6$ van der Waals coefficients, as shown by the application to a set of selected dimers. Preliminary results on Ar on graphite and Ne on the Cu(111) metal surface suggest that also the $C_3$ coefficients, characterizing molecule-surfaces van der Waals interactions are better estimated with the new scheme.