An ``extended'' version of symmetry-adapted perturbation theory (XSAPT), developed in our group over the past several years, extends traditional SAPT to noncovalent clusters larger than dimers, affording accurate noncovalent interaction energies and energy decomposition analysis. The original implementation of XSAPT is based on ``ChElPG'' charges that are fit to reproduce molecular electrostatic potentials, and this becomes a computational bottleneck in large systems. We introduce an alternative charge embedding, based on modified Hirshfeld atomic charges, which dramatically lowers the computational cost without significant effect on accuracy. This is especially beneficial in XSAPT calculations where the monomer units are large, and we present calculations on systems such as a DNA intercalation complex and binding of a drug molecule to an enzyme. The new embedding scheme is also useful for performing Ewald summation in QM/MM calculations with periodic boundary conditions.

Novel charge embedding scheme for Extended Symmetry-Adapted Perturbation Theory (XSAPT)

2019 Spring National Meeting

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