A new parametrizable model of molecular electronic structure

TL;DR

This paper introduces a parametrizable electronic structure model that combines elements of Hartree-Fock and perturbation theory, trained on extensive coupled-cluster data, aiming for improved accuracy in large molecular systems at low computational cost.

Contribution

The paper presents a novel, parametrized electronic structure model that incorporates polarization effects and links to correlated wavefunction theory, trained on a large dataset of molecules.

Findings

Good agreement with coupled-cluster reference data

Enhanced dipole polarizabilities and intermolecular potentials

Potential for studying large molecular systems efficiently

Abstract

A new electronic structure model is developed in which the ground state energy of a molecular system is given by a Hartree-Fock-like expression with parametrized one- and two-electron integrals over an extended (minimal + polarization) set of orthogonalized atom-centered basis functions, the variational equations being solved formally within the minimal basis but the effect of polarization functions being included in the spirit of second-order perturbation theory. It is designed to yield good dipole polarizabilities and improved intermolecular potentials with dispersion terms. The molecular integrals include up to three-center one-electron and two-center two-electron terms, all in simple analytical forms. A method to extract the effective one-electron Hamiltonian of nonlocal-exchange Kohn-Sham theory from the coupled-cluster one-electron density matrix is designed and used to get its matrix representation in a molecule-intrinsic minimal basis as an input to the paramtrization procedure -- making a direct link to the correlated wavefunction theory. The model has been trained for 15 elements (H, Li--F, Na--Cl, 720 parameters) on a set of 5581 molecules (including ions, transition states, and weakly-bound complexes) whose first- and second-order properties were computed by the coupled-cluster theory as a reference, and a good agreement is seen. The model looks promising for the study of large molecular systems, it is believed to be an important step forward from the traditional semiempirical models towards higher accuracy at nearly as low a computational cost.