Force correcting atom centered potentials for generalized gradient approximated density functional theory: Approaching hybrid functional accuracy for geometries and harmonic frequencies in small chlorofluorocarbons

TL;DR

This paper introduces empirical force correcting atom centered potentials (FCACPs) to improve GGA DFT accuracy for geometries and frequencies in small chlorofluorocarbons, approaching hybrid functional performance.

Contribution

The study develops transferable FCACPs parameterized for each atom type to correct GGA DFT calculations, enhancing accuracy for molecular geometries and vibrational frequencies.

Findings

GGA+FCACP significantly improves harmonic frequency predictions.

The method reduces overestimated polarizabilities.

Transferability is demonstrated across various chlorofluorocarbon molecules.

Abstract

Generalized gradient approximated (GGA) density functional theory (DFT) typically overestimates polarizability and bond-lengths, and underestimates force constants of covalent bonds. To overcome this problem we show that one can use empirical force correcting atom centered potentials (FCACPs), parameterized for every nuclear species. Parameters are obtained through minimization of a penalty functional that explicitly encodes hybrid DFT forces and static polarizabilities of reference molecules. For hydrogen, fluorine, chlorine, and carbon the respective reference molecules consist of H$_2$, F$_2$, Cl$_2$, and CH$_4$. The transferability of this approach is assessed for harmonic frequencies in a small set of chlorofluorocarbon molecules. Numerical evidence, gathered for CF$_4$, CCl$_4$, CCl$_3$F, CCl$_2$F$_2$, CClF$_3$, ClF, HF, HCl, CFH$_3$, CF$_2$H$_2$, CF$_3$H, CHCl$_3$, CH$_2$Cl$_2$, CH$_3$Cl indicates that the GGA+FCACP level of theory yields harmonic frequencies that are significantly more consistent with hybrid DFT values, as well as slightly reduced molecular polarizability.