This publication combines forces and expertise of the Isborn, Hratchian, Pribram-Jones, and Shi groups, along with great contributions from Tim and Duncan! This study led by Ali and Shao-Yu examines the behavior of the widely used LR-TDDFT approach and the recently developed PIMOM △SCF framework for computing the excited states and vibronic absorption spectra for the methylene blue chromophore. Our study shows how the nature of the adiabatic excited states produced by LR-TDDFT can lead to Hessian based vibronic spectra that are very different from those obtained with vertical gradient and ab initio molecular dynamics based approaches. The results presented advocate the ability of recently developed PIMOM △SCF approach to approximate excited states and Hessian based absorption spectra that are not as sensitive to state mixing. Multiple alternatives to the widely-used adiabatic Hessian LR-TDDFT approach are proposed.

This publication combines forces and expertise of the Isborn, Hratchian, Pribram-Jones, and Shi groups, along with great contributions from Tim and Duncan! This study led by Ali and Shao-Yu examines the behavior of the widely used LR-TDDFT approach and the recently developed PIMOM △SCF framework for computing the excited states and vibronic absorption spectra for the methylene blue chromophore. Our study shows how the nature of the adiabatic excited states produced by LR-TDDFT can lead to Hessian based vibronic spectra that are very different from those obtained with vertical gradient and ab initio molecular dynamics based approaches. The results presented advocate the ability of recently developed PIMOM △SCF approach to approximate excited states and Hessian based absorption spectra that are not as sensitive to state mixing. Multiple alternatives to the widely-used adiabatic Hessian LR-TDDFT approach are proposed.