Ab Initio Molecular Dynamics with Equation-of-Motion Coupled-Cluster Theory: Electronic Absorption Spectrum of Ethylene

K. K. Baeck and T. J. Martinez

The equation-of-motion coupled-cluster (EOM-CCSD) method has been combined with the full multiple-spawning (FMS) method to include dynamic electron correlation effects in ab initio excited state dynamics. We use a quasi-diabatic scheme to follow adiabatic states, demanding smooth variation of the EOM-CCSD energy and oscillator strength. The potential energy surfaces computed "on-the-fly" are used in the simulation of electronic absorption spectra. We compute absorption spectra of ethylene for the Rydberg p→3s and valence p→p* states, and compare directly to experimental results. Good agreement is obtained in the 50 000–70 000 cm-1 range.