Derivative couplings are the essential quantities at the interface between electronic-structure calculations and nonadiabatic dynamics. Unfortunately, standard approaches for calculating these couplings usually neglect electronic motion, which can lead to spurious electronic transitions. Here we provide a general framework for correcting these anomalies by incorporating perturbative electron-translation factors (ETFs) into the atomic-orbital basis. For a range of representative organic molecules, we find that our ETF correction is often small but can be qualitatively important, especially for few-atom systems or highly symmetric molecules. Our method entails no additional computational cost, such that ETFs are “built-in,” and it is equivalent to a simple rule of thumb: We should set the antisymmetrized version of the nuclear overlap-matrix derivative to zero wherever it appears. Thus, we expect that built-in ETFs will be regularly incorporated into future studies of nonadiabatic dynamics.
Fatehi, S.; Subotnik, J. E. Derivative Couplings with Built-In Electron-Translation Factors: Application to Benzene. J. Phys. Chem. Lett. 2012, 3, 2039– 2043, DOI: 10.1021/jz300617
The Journal of Physical Chemistry Letters