Removing the deadwood from DFT/MRCI wave functions: The p-DFT/MRCI method

TL;DR

The paper introduces p-DFT/MRCI, a configuration pruning method that significantly reduces computational cost of DFT/MRCI calculations by removing superfluous configurations without sacrificing accuracy.

Contribution

It presents a simple perturbation-based pruning algorithm that enhances DFT/MRCI efficiency, enabling faster excited state calculations for large molecules.

Findings

Orders of magnitude computational savings

Retains original DFT/MRCI accuracy

Effective removal of superfluous configurations

Abstract

The combined density functional theory and multireference configuration interaction (DFT/MRCI) method is a powerful tool for the calculation of excited electronic states of large molecules. There exists, however, a large amount of superfluous configurations in a typical DFT/MRCI wave function. We show that this deadwood may be effectively removed using a simple configuration pruning algorithm based on second-order Epstein-Nesbet perturbation theory. The resulting method, which we denote p-DFT/MRCI, is shown to result in orders of magnitude saving in computational timings, while retaining the accuracy of the original DFT/MRCI method.