Evaluating the interactions between vibrational modes and electronic transitions using frontier orbital energy derivatives

Vibrations affect molecular optoelectronic properties, even at zero kelvin. Accounting for these effects using computational modelling is costly, as it requires many calculations at geometries distorted from equilibrium. Here, we propose a low-cost method for identifying vibrations most strongly coupled to the electronic structure, based on using orbital energy derivatives as a diagnostic. Frontier orbital energy derivatives can be used to identify vibrations strongly coupled to electronic structure.