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The Pole Structure of the Dynamical Polarizability Tensor in Equation-of-Motion Coupled-Cluster Theory

preprint
submitted on 26.08.2018, 07:07 and posted on 27.08.2018, 13:40 by Kaushik Nanda, Anna Krylov, Jürgen Gauss
In this Letter, we investigate the pole structure of dynamical polarizabilities computed within the equation-of-motion coupled-cluster (EOM-CC) theory. We show, both theoretically and numerically, that approximate EOM-CC schemes such as, for example, the EOM-CC singles and doubles (EOM-CCSD) model exhibit an incorrect pole structure in which the poles that reflect the excitations from the target state (i.e., the EOM-CC state) are supplemented by artificial poles due to excitations from the coupled-cluster (CC) reference state. These artificial poles can be avoided
by skipping the amplitude response and reverting to a sum-over-states formulation. While numerical results are generally in favor of such a solution, its major drawback
is that this scheme violates size extensivity.

History

Email Address of Submitting Author

knanda@usc.edu

Institution

University of Southern California

Country

United States

ORCID For Submitting Author

0000-0002-3447-6678

Declaration of Conflict of Interest

None

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