Time-dependent equation-of-motion coupled-cluster (TD-EOM-CC) and its applications
Young Choon Parka, Ajith Pererab, and Rodney J. Bartlettb
a Korea Institute of Fusion Energy
b Quantum Theory Project, University of Florida
Time-dependent equation-of-motion coupled-cluster (TD-EOM-CC) and its applications
Young Choon Parka, Ajith Pererab, and Rodney J. Bartlettb
a Korea Institute of Fusion Energy
b Quantum Theory Project, University of Florida
The equation-of-motion coupled-cluster (EOM-CC) method is widely recognized for providing accurate excitation energies, encompassing not only valence excitations but also Rydberg and core electron transitions. Recently, we have implemented a time-dependent version of the EOM-CC method (TD-EOM-CC). While the conventional (time-independent) EOM-CC approach is obtained from the diagonalization of the molecular Hamiltonian, TD-EOM-CC achieves excitation spectra by the time-propagation of an operator, typically the dipole, and calculating the autocorrelation with respect to this propagation. The Fourier transform of the resulting autocorrelation function yields the electronic excitation spectra. The TD-EOM-CC approach provides access to a broader range of electronic excitation spectra, whereas conventional EOM-CC often encounters challenges, particularly in converging higher excited states.
In this presentation, we demonstrate the application of TD-EOM-CC to various gas-phase molecules, evaluating its reliability for both valence and core excitations. As with EOM-CC, TD-EOM-CC proves to be a reliable computational approach, especially in cases lacking experimental data. We further compare TD-EOM-CC results with those obtained using real-time time-dependent density functional theory (RT-TDDFT) to assess their consistency. Finally, we briefly discuss the extension of TD-EOM-CC spectra calculations to multipole moments, including electronic quadrupole moments.