Electron-proton correlation for hydrogen tunneling systems

Hydrogen tunneling is important for numerous chemical and biological processes. We study this phenomenon with a multiconfigurational nuclear-electronic orbital approach. Our results demonstrate that a single configuration nuclear-electronic wave function is inadequate to describe hydrogen tunneling systems because such wave functions do not include the essential electron-proton correlation. A state-averaged multiconfigurational approach is proposed as a practical method for potentially including sufficient electron-proton correlation to obtain delocalized nuclear-electronic wave functions for these systems.