Reliable transition properties from excited-state mean-field calculations

TL;DR

This paper evaluates the delta-SCF method for predicting excited-state properties, especially transition dipole moments, and introduces a correction for origin dependence to improve reliability in spectral calculations.

Contribution

The study benchmarks delta-SCF on a larger molecular set and proposes a simple orthogonalization correction for more accurate transition dipole predictions.

Findings

Delta-SCF predicts excitation energies effectively.

The orthogonalization correction reduces origin dependence.

Application to bacteriochlorophyll demonstrates practical utility.

Abstract

Delta-self-consistent field theory (delta-SCF) is a conceptually simple and computationally inexpensive method for finding excited states. Using the maximum overlap method to guide optimization of the excited state, delta-SCF has been shown to predict excitation energies with a level of accuracy that is competitive with, and sometimes better than, that of TDDFT. Here we benchmark delta-SCF on a larger set of molecules than has previously been considered, and, in particular, we examine the performance of delta-SCF in predicting transition dipole moments, the essential quantity for spectral intensities. A potential downfall for delta-SCF transition dipoles is origin dependence induced by the nonorthogonality of delta-SCF ground and excited states. We propose and test the simplest correction for this problem, based on symmetric orthogonalization of the states, and demonstrate its use on bacteriochlorophyll structures sampled from the photosynthetic antenna in purple bacteria.