Abstract
We describe a method for including van der Waals (vdW) interactions in Density Functional Theory (DFT) using the Maximally-Localized Wannier functions (MLWFs), which is free from empirical parameters. With respect to the previous DFT/vdW-WF2 version, in the present DFT/vdW-WF2-x approach, the empirical, short-range, damping function is replaced by an estimate of the Pauli exchange repulsion, also obtained by the MLWFs properties. Applications to systems contained in the popular S22 molecular database and to the case of adsorption of Ar on graphite, and Xe and water on graphene, indicate that the new method, besides being more physically founded, also leads to a systematic improvement in the description of systems where vdW interactions play a significant role.
Highlights
Density Functional Theory (DFT) is a well-established computational approach to study the structural and electronic properties of condensed matter systems from first principles
Current, approximated density functionals allow a quantitative description at much lower computational cost than other first principles methods, they fail[1] to properly describe dispersion interactions. These forces originate from correlated charge oscillations in separate fragments of matter and the leading component is represented by the R−6 van der Waals interaction[2], due to correlated instantaneous dipole fluctuations. vdW interactions play a fundamental role in determining the structure, stability, and function of a wide variety of systems, including molecules, clusters, proteins, nanostructured materials, molecular solids and liquids, and in adsorption processes of fragments weakly interacting with a substrate (”physisorbed”)
In a recent paper[24] we have presented a new method, named DFT/vdW-WF2-x, to overcome the above limitation, where the empirical, short-range, damping function is replaced by an estimate of the Pauli exchange repulsion, obtained by the Maximally Localized Wannier Functions (MLWFs) properties
Summary
Density Functional Theory (DFT) is a well-established computational approach to study the structural and electronic properties of condensed matter systems from first principles. A family of such methods, all based on the Maximally Localized Wannier Functions (MLWFs)[10], has been developed, namely the original DFT/vdW-WF scheme[11,12,13], DFT/vdW-WF2[14] (based on the London expression and taking into account the intrafragment overlap of the MLWFs), DFT/vdWWF2s[15] (including metal-screening corrections), and DFT/vdW-QHO-WF[16] (adopting the coupled Quantum Harmonic Oscillator model), successfully applied to a variety of systems [11,12,13,14,15,16,17,18,19,20,21,22,23]: small molecules, water clus- In all these methods a certain degree of empiricism is present since the energetic vdW-correction term is multiplied by a short-range damping function, which is introduced to avoid the unphysical divergence of the vdW correction at small fragment separations, and to eliminate double countings of correlation effects ( standard DFT approaches are able to describe short-range correlations). This damping function contains one or more empirical parameters which are typically set by a trial and error approach or/and are fitted using some reference database
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