Van der Waals contributions

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General

Ar dimer binding energy curve.
Binding energy of the Ar dimer.

Ubiquitous Van der Waals interactions between atoms and molecules are important for many molecular and solid structures. These systems are often studied from first principles using the Density Functional Theory (DFT). However, the commonly used DFT functionals fail to capture the essence of Van der Waals effects. Most attempts to correct for this problem have a basic semiempirical character, although computationally more expensive first principles schemes have been recently developed. Of course, the key issue is finding a way to include Van der Waals interactions in DFT without dramatically increasing the computational cost.

The present DFT/vdW-WF approach, based on the use of the Maximally-Localized Wannier functions, tries to combine the simplicity of the semiempirical formalism with the accuracy of the first principles approaches, and appears to be promising, being simple, efficient, accurate, and transferable (for instance, charge polarization effects are naturally included), also considering that the method is free from system-dependent fitted parameters. It has been successfully applied to small molecules, water clusters, bulk systems (Ar,graphite), carbon nanotubes, atoms and fragments (He, Ne, Ar, Kr, Xe, H2, H2O, water layers) weakly bonded (physisorbed) to metal (Al(100), Al(111), Cu(111), Pb(111)), semimetal (graphite/graphene) and other (Cl- and H-terminated Si(111)) surfaces.

The new DFT/vdW-WF2 version is based on the simpler London expression and takes into account the intrafragment overlap of the localized Wannier functions, leading to a considerable improvement in the evaluation of the C6 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 C3 coefficients, characterizing molecule-surfaces van der Waals interactions are better estimated with the new scheme.

Contributors

Pier Luigi Silvestrelli

Dipartimento di Fisica
Universita' di Padova, Italy
tel. +39 049 8277171
fax +39 049 8277102
e-mail: psil.AT.pd.infm.it

Alberto Ambrosetti

Fritz Haber Institute,
Berlin, Germany
tel. +49 30 8413 4814
e-mail: ambrosetti.AT.fhi-berlin.mpg.de

References (Theory & Applications)

DFT/vdW-WF method

DFT/vdW-WF2 method

Applications


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