Direct location of the minimum point on intersection seams of potential energy surfaces with equation-of-motion coupled-cluster methods

Abstract

An implementation of the projected gradient method for locating the minimum energy crossing point between electronic states of different symmetry/multiplicity within the equation-of-motion coupled-cluster family of methods is reported. The method is applied to characterize the intersections between electronic states in , NO₂, and para-benzyne using the excitation energies, ionization potential, and spin-flip variants of the equation-of-motion coupled-cluster methods. The performance of the algorithm is discussed and recommendations for improving the convergence in problematic situations are given.

Keywords:

• MECP
• Conical intersections
• Equation-of-motion
• Coupled-cluster
• Analytic gradients

Acknowledgements

This work was supported by the Department of Energy (DE-FG02-05ER15685). We also acknowledge the use of the resources of the Center for Computational Studies of Electronic Structure and Spectroscopy of Open-Shell and Electronically Excited Species (iopenshell.usc.edu) supported by the National Science Foundation through the CRIF:CRF CHE-0625419+0624602+0625237 grant.