Generalized Polarizabilities (GPs) describe the quadratic response of a system to arbitrary perturbations by the external electric potential. The widely invoked density response function is a special case of GPs where the perturbations are delta functions. GPs speed up the calculation of Quantum/Molecular Mechanics (QM/MM) energies by 4-5 orders of magnitude through replacing the solution of the Schrödinger equation for the electrically perturbed molecule with the calculation of polarization energies, using precalculated GPs. Accurate QM/MM simulations of entropic quantities for potential surfaces are still expensive because of the need for extensive ensemble averaging. We show that the generalized polarizability matrix can be approximated by a strongly reduced (~10 % ) set of its principal components, the <i>natural polarization functions</i>. Given the quadratic scaling of the computational effort with the number of polarization functions, this truncation yields further orders-of-magnitude savings. Natural polarization functions provide the most compact description of molecular polarizability in an arbitrary electric potential and will be compared to similar recent methods aimed to accelerate the calculation of polarization energies. Natural polarization functions can be localized to atoms, giving distributed atomic polarizabilities which do not involve arbitrary partitioning of the molecule to atomic regions.

Natural representation of molecular polarizability for efficient QM/MM simulations

2019 Spring National Meeting

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