We present an improved approach for generating a set of optimized frontier orbitals (HOMO and LUMO) that minimizes the energy of one double configuration. We further benchmark the effect of including such a double within a CIS or TD-DFT configuration interaction Hamiltonian for a set of test cases. We find that, although we cannot achieve quantitative accuracy, the algorithm is quite robust and routinely delivers an enormous qualitative improvement to standard single-reference electronic structure calculations.
@article{arxiv.2104.07154,
title = {On The Inclusion of One Double Within CIS and TD-DFT},
author = {Vishikh Athavale and Hung-Hsuan Teh and Joseph Subotnik},
journal= {arXiv preprint arXiv:2104.07154},
year = {2022}
}