One primary bottleneck for the quantitative treatment of internal conversion is the evaluation of nuclear-coordinatedependent wavefunction components . Formal generation of vibronic coupling requires the mixing of nuclear-electronic and nuclear-vibrational wavefunctions, and is a relatively nontrivial photophysical property to predict. A consequence of this complexity makes it so that many choose to instead infer the rate of internal conversion from other quantum chemical properties as opposed to calculating it directly. Erker & Basché infer the rate of internal conversion in dibenzoterrylene as a function of the photoluminescent quantum yield P LQY , cast as :