where σ F C j is the FTFC absorption/emission spectrum of each snapshot computed with optimized chromophore geometry, R i,opt for reference electronic state i. Temperature effects of the chromophore are modeled through the population of the vibrational energy levels within the FTFC lineshape function, whereas temperature effects of the solvent are modeled classically using MD. Although straightforward, this E-sumFTFC approach is computationally expensive as within an adiabatic Hessian approach it requires geometry optimization for both ground and excited states, along with computation of the corresponding normal modes.