A perturbative approximation to DFT/MRCI: DFT/MRCI(2)
Abstract
We introduce a perturbative approximation to the combined density functional theory and multireference configuration interaction (DFT/MRCI) method. The method, termed DFT/MRCI(2), results from the application of quasi-degenerate perturbation theory and the Epstein-Nesbet partitioning of the DFT/MRCI Hamiltonian matrix. This results in the replacement of the diagonalization of the large DFT/MRCI Hamiltonian with that of a small effective Hamiltonian, and affords orders of magnitude savings in terms of computational cost. Moreover, the DFT/MRCI(2) approximation is found to be of excellent accuracy, furnishing excitation energies with a root mean squared deviation from the DFT/MRCI values of less than 0.03 eV for an extensive test set of organic molecules.
Cite
@article{arxiv.2208.02365,
title = {A perturbative approximation to DFT/MRCI: DFT/MRCI(2)},
author = {Simon P. Neville and Michael S. Schuurman},
journal= {arXiv preprint arXiv:2208.02365},
year = {2022}
}