A new framework for frequency-dependent polarizable force fields

TL;DR

This paper introduces ACKS2ω, a frequency-dependent polarizable force field extension that accurately predicts dynamical response properties and dispersion coefficients, bridging quantum mechanics and efficient force-field modeling.

Contribution

The paper presents ACKS2ω, a novel frequency-dependent extension of ACKS2, enabling efficient and accurate prediction of molecular response properties and dispersion coefficients.

Findings

ACKS2ω accurately reproduces TDDFT absorption spectra.

The model achieves a 3.84% MAPE against experimental data.

Atomic monopoles and dipoles suffice for accurate modeling.

Abstract

A frequency-dependent extension of the polarizable force field ``Atom-Condensed Kohn-Sham density functional theory approximated to the second-order'' (ACKS2) [J. Chem. Phys. 141, 194114 (2014)] is proposed, referred to as ACKS2$\omega$. The method enables theoretical predictions of dynamical response properties of finite systems after a partitioning of the frequency-dependent molecular response function. Parameters in this model are computed simply as expectation values of an electronic wavefunction, and the hardness matrix is entirely reused from ACKS2 as an adiabatic approximation is used. A numerical validation shows that accurate models can already be obtained with atomic monopoles and dipoles. Absorption spectra of 42 organic and inorganic molecular monomers are evaluated using ACKS2$\omega$, and our results agree well with the time-dependent DFT calculations. Also for the calculation of $C_6$ dispersion coefficients, ACKS2$\omega$ closely reproduces its TDDFT reference. When parameters for ACKS2$\omega$ are derived from a PBE/aug-cc-pVDZ ground state, it reproduces experimental values for 903 organic and inorganic intermolecular pairs with an MAPE of 3.84\%. Our results confirm that ACKS2$\omega$ offers a solid connection between the quantum-mechanical description of frequency-dependent response and computationally efficient force-field models.