posted on 2018-11-27, 00:00authored byZsuzsanna Benda, Thomas-C. Jagau
We
present a method for locating non-Hermitian degeneracies, called
exceptional points (EPs), and minimum-energy EPs between molecular
resonances using the complex absorbing potential equation-of-motion
coupled-cluster (CAP-EOM-CC) method. EPs are the complex-valued analogue
of conical intersections (CIs) and have a similar impact on nonadiabatic
processes between resonances as CIs have on nonradiative transitions
between bound states. We demonstrate that the CAP-EOM-CC method in
the singles and doubles approximation (CAP-EOM-CCSD) yields crossings
of the correct dimensionality. The use of analytic gradients enables
applications to multidimensional problems. Results are presented for
hydrogen cyanide and chloroethylene, for which the location of the
crossings of anionic resonances is crucial for understanding the dissociative
electron attachment process.