Charge-transfer from Regularized Symmetry-Adapted Perturbation Theory

TL;DR

This paper introduces a physically motivated, basis-independent method to isolate and quantify charge-transfer energy in intermolecular interactions using regularized SAPT, improving the understanding and modeling of charge transfer phenomena.

Contribution

It proposes a novel regularized SAPT approach to define charge-transfer energy as a tunneling phenomenon, enabling basis-independent and more accurate analysis.

Findings

Provides a basis-independent definition of charge-transfer energy.

Captures asymmetry and secondary effects in charge transfer.

Enables more confident damping in polarization models.

Abstract

The charge-transfer (CT) together with the polarization energy appears at second and higher orders in symmetry-adapted perturbation theory (SAPT). At present there is no theoretically compelling way of isolating the charge-transfer energy that is simultaneously basis-set independent and applicable for arbitrary intermolecular separation. We argue that the charge-transfer can be interpreted as a tunneling phenomenon, and can therefore be defined via regularized SAPT. This leads to a physically convincing, basis-independent definition of the charge-transfer energy that captures subtleties of the process, such as the asymmetry in the forward and backward charge transfer, as well as secondary transfer effects. With this definition of the charge-transfer the damping needed for polarization models can be determined with a level of confidence hitherto not possible.