A Flexible, Automated, and Basis-Set Insensitive Domain-Based Charge-Transfer Decomposition for Correlated Wavefunctions and its Application to Inter- and Intramolecular Cases

TL;DR

This paper introduces a versatile, automated charge-transfer decomposition method compatible with various wavefunctions, providing basis-set insensitive analysis of excited states and CT contributions in molecular systems.

Contribution

The authors develop a new domain-based CT decomposition framework that is flexible, automated, and basis-set insensitive, applicable to any CI-type excited-state wavefunction.

Findings

The method accurately dissects local and CT excitations in inter- and intramolecular cases.

CT character remains largely basis-set independent across different schemes.

The framework yields consistent results with different domain-accumulation strategies.

Abstract

We present a flexible, automated, and basis-set insensitive domain-based charge-transfer (CT) decomposition framework that can be combined with any CI-type excited-state wavefunction. Our approach is not based on excited-state densities and allows the excited-state character to be dissected into local and domain-based CT excitations and measures the individual contributions to each excited state. To guarantee a broad applicability, we introduce two domain-accumulation strategies to translate hole-particle substitutions to domain-domain excitations: a strict domain partitioning and a weighted approach suitable for small molecules and a large number of domains. The performance of both schemes is assessed for inter- and intramolecular CT excitations and various basis sets using EOM-CCSD and its simplified counterpart EOM-pCCD+S. Most importantly, the CT character is, to a large extent, basis-set independent, and both domain-accumulation schemes give consistent results. Overall, our framework provides a robust CT analysis and a domain resolution of the excitation character for a variety of computational setups and excited-state models.