Tight-Binding Approximations to Time-Dependent Density Functional Theory - a fast approach for the calculation of electronically excited states

TL;DR

The paper introduces TD-DFT+TB, a fast and broadly applicable method combining DFT and tight binding approximations to accurately compute electronically excited states, matching the accuracy of more expensive TD-DFT calculations.

Contribution

It presents TD-DFT+TB, a novel approach that improves excitation energy calculations without relying on DFTB parametrization, enabling application to all element combinations.

Findings

UV/Vis spectra match TD-DFT results

Vertical excitation energy errors halved compared to TD-DFTB

Applicable to systems with all element combinations

Abstract

We propose a new method of calculating electronically excited states that combines a density functional theory (DFT) based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive time-dependent density functional theory (TD-DFT) calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB.