Assessment of Low Scaling Approximations to EOM-CCSD Method for Ionization Potential

TL;DR

This study evaluates various low-scaling approximations to the EOM-CCSD method for ionization potential calculations, revealing inconsistent performance across different ionized states and highlighting the limitations of these approximations.

Contribution

It provides a comparative analysis of approximate EOM-CCSD variants against EOM-CCSDT, emphasizing their variable accuracy for different ionization types.

Findings

Approximate variants show non-uniform errors across ionization types.

None of the approximations consistently outperform others.

Performance depends on the specific nature of the approximation used.

Abstract

In this paper, we investigate the performance of different approximate variants of the EOM-CCSD method for calculation of ionization potential, as compared to EOM-CCSDT reference values. The errors in the various approximate variants of the EOM-CCSD method are quite different for different kind of ionized states. None of the approximate variants including the original EOM-CCSD method gives a uniform performance over outer valence, inner valence, and core ionization, favoring one or other, depending upon nature of the approximation used.