Abstract
van der Waals (vdW) dispersion interactions strongly impact the properties of molecules and materials. Often, the description of vdW interactions should account for the coupling with pervasive electric fields, stemming from membranes, ionic channels, liquids, or nearby charged functional groups. However, this quantum-mechanical effect has been omitted in atomistic simulations, even in widely employed electronic-structure methods. Here, we develop a model and study the effects of an external charge on long-range vdW correlations. We show that a positive external charge stabilizes dispersion interactions, whereas a negative charge has an opposite effect. Our analytical results are benchmarked on a series of (bio)molecular dimers and supported by calculations with high-level correlated quantum-chemical methods, which estimate the induced dispersion to reach up to 35% of intermolecular binding energy (4 kT for amino-acid dimers at room temperature). Our analysis bridges electrostatic and electrodynamic descriptions of intermolecular interactions and may have implications for non-covalent reactions, exfoliation, dissolution, and permeation through biological membranes.
Highlights
In addition to internal permanent and fluctuating electrostatic moments, molecules are substantially affected by external electric fields of various origins
We will refer to the van der Waals (vdW) part of intermolecular correlation energy that is modified by an external charge as field-induced dispersion (FID)
Our analysis demonstrates the possibility of tailoring intermolecular van der Waals dispersion interactions with external electric charges
Summary
In addition to internal permanent and fluctuating electrostatic moments, molecules are substantially affected by external electric fields of various origins. The calculation of FID energies requires the development of quantum-mechanical techniques beyond second-order perturbation theory and simultaneously consider multipole expansion terms beyond the dipole approximation in the treatment of electronic correlation This allows to account for the effect of an electric field on excited states, while conventional DFT + vdW approaches capture influence of electric field on static density only. We generalize the treatment of vdW interactions to include the effect of an inhomogeneous electric field and demonstrate an analytical method of evaluating the FID contribution to binding energies, bridging electrostatic and electrodynamic models of intermolecular interactions This paves the way to efficiently include FID energies in classical force fields and electronic-structure calculations
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