Implementation and benchmark of a long-range corrected functional in the density functional based tight-binding method

TL;DR

This paper implements a long-range corrected functional within the density functional based tight-binding (DFTB) method, enabling more accurate predictions for spectra and thermochemistry while maintaining computational efficiency.

Contribution

It introduces the first implementation of a long-range corrected functional in DFTB and benchmarks its performance against higher-level methods.

Findings

Cures overpolarization issues in electric fields for DFTB

Maintains computational efficiency comparable to original DFTB

Improves accuracy of ionization potentials and electron affinities

Abstract

Bridging the gap between first principles methods and empirical schemes, the density functional based tight-binding method (DFTB) has become a versatile tool in predictive atomistic simulations over the past years. One of the major restrictions of this method is the limitation to local or gradient corrected exchange-correlation functionals. This excludes the important class of hybrid or long-range corrected functionals, which are advantageous in thermochemistry, as well as in the computation of vibrational, photoelectron and optical spectra. The present work provides a detailed account of the implementation of DFTB for a long-range corrected functional in generalized Kohn-Sham theory. We apply the method to a set of organic molecules and compare ionization potentials and electron affinities with the original DFTB method and higher level theory. The new scheme cures the significant overpolarization in electric fields found for local DFTB, which parallels the functional dependence in first principles density functional theory (DFT). At the same time the computational savings with respect to full DFT calculations are not compromised as evidenced by numerical benchmark data.