The effective fragment potential method (EFP) is a quantum mechanics/molecular mechanics (QM/MM) approach developed as a nonempirical alternative to force-field based QM/MM methods.  In EFP, one describes (relatively weak) intermolecular interactions using perturbation theory starting from the noninteracting (unperturbed) fragments.  The intermolecular interaction can be represented as a series of short- and long-range terms. Long-range interactions, which are proportional to the distance according to 1/Rn, include Coulomb, induction (polarization), and dispersion terms, whereas short-range interactions that depend on the interfragment density overlaps consist of exchange-repulsion, charge-transfer, and screening terms.  The expression for exchange-repulsion involves overlap and kinetic energy integrals between pairs of localized orbitals.  These integrals make the exchange-repulsion the most computationally expensive part of EFP energy calculations in moderately sized systems.  Removing the exchange-repulsion integrals from EFP by parameterizing the method would increase the speed of EFP by a factor of ten or more.

Parameterization of the exchange-repulsion term of effective fragment potential

244th National Meeting (2012)

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