Within the E opt -avgFTFC approach, the vibrational frequencies and a full vibronic spectrum are not calculated for each snapshot, and therefore ω 00 that measures the energy difference between the zero-point energies of the ground and excited state for each snapshot is not available. The question then arises -How will the placement of the average FC lineshape be determined, given that we only have the VEE/VDEs for each snapshot? Generally, the VEE is higher in energy than ω 00 , and the VDE energy is lower in energy than ω 00 . For placement of the average FC lineshape for each snapshot at an energy approximating ω 00 for that snapshot, we determined an energetic shift value as the average value of the difference between the VEE/VDE and ω 00 for the snapshots used in the average FTFC lineshape calculation: (ω if -ω 00 ) FC . This value is positive for absorption and negative for emission. The average FTFC lineshape is then aligned with its ω 00 at the value of the vertical excitation/deexcitation energy for each snapshot shifted by (ω if -ω 00 ) FC , and the spectra are summed to create the E opt -avgFTFC spectrum as