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arXiv · 2606.13849

Oscillator Strengths and Transition Dipole Moments from a Simplified Equation-of-Motion Coupled Cluster Formalism within the Frozen-Pair Approximation

Seyedehdelaram Jahani·Katharina Boguslawski·Pawel Tecmer
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Abstract

In this work, we derive the working equations for the transition density matrices within the equation-of-motion frozen-pair coupled-cluster framework. We focus specifically on the recently developed EOM-fpCCSD and EOM-ptCCSD models and present the corresponding transition dipole moments and oscillator strengths obtained via approximate expressions. This formulation avoids the computational overhead of solving the coupled-cluster $\Lambda$ equations. Furthermore, we employ a matrix inverse approximation to eliminate the need for explicit calculation of the left EOM eigenvectors. The accuracy of the resulting EOM-fpCCD and EOM-ptCCSD excited-state properties is benchmarked against the linear-response (LR)-CCSD method. Our results demonstrate that the description of excited state properties is improved when using EOM-fpCCSD and EOM-ptCCSD models compared to the standard EOM-CCSD variant.

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Seyedehdelaram Jahani, Katharina Boguslawski, Pawel Tecmer. 2026-06-11. Oscillator Strengths and Transition Dipole Moments from a Simplified Equation-of-Motion Coupled Cluster Formalism within the Frozen-Pair Approximation. https://arxiv.org/abs/2606.13849

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