Crossing conditions in coupled cluster theory

Author
Kjønstad, Eirik F · Myhre, Rolf H · Martinez, Todd J · Koch, Henrik
Year 2017
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Abstract

We derive the crossing conditions at conical intersections between electronic states in coupled cluster theory, and show that if the coupled cluster Jacobian matrix is nondefective, two (three) independent conditions are correctly placed on the nuclear degrees of freedom for an inherently real (complex) Hamiltonian. Calculations using coupled cluster theory on an $2 {^{1}}A' / 3 {^{1}}A'$ conical intersection in hypofluorous acid illustrate the nonphysical artifacts associated with defects at accidental same-symmetry intersections. In particular, the observed intersection seam is folded about a space of the correct dimensionality, indicating that minor modifications to the theory are required for it to provide a correct description of conical intersections in general. We find that an accidental symmetry allowed $1 {^{1}}A" / 2 {^{1}}A"$ intersection in hydrogen sulfide is properly described, showing no artifacts as well as linearity of the energy gap to first order in the branching plane.

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Details

Title
Crossing conditions in coupled cluster theory
Author
Kjønstad, Eirik F · Myhre, Rolf H · Martinez, Todd J · Koch, Henrik
Year
2017
Type
Research Article
Language
eng
Comment
9 pages and 4 figures
History
2017-08-03 00:00:00
Categories
Chemical Physics
This is Version 1 of this record. We added this version on August 5, 2017. This version is based on an original data import from arXiv.org e-Print archive.