Nuclear quantum effects such as zero-point energy and hydrogen tunneling play an important role in a wide range of chemical reactions, especially those involving hydrogen bonding and hydrogen transfer. Moreover, non-Born-Oppenheimer effects are important in reactions such as proton-coupled electron transfer. The breakdown of the Born-Oppenheimer approximation between electronic and nuclear motions engenders the need for the development of quantum chemical methods that can accurately account for electron-proton nonadiabatic effects.  The nuclear-electronic orbital (NEO) method is an orbital-based approach that inherently includes electron-proton nonadiabaticity by treating electrons and select protons quantum mechanically on equal footing. We have previously developed mean-field and explicitly-correlated methods to account for electron-proton interactions. Here, we present a hybrid of these two approaches in which explicit correlation is included only between the relevant nuclei and a subspace of the electronic orbitals. We demonstrate the practical advantages of this method and describe representative examples.

Accurately accounting for important electron-proton interactions using explicitly-correlated wavefunctions within the nuclear-electronic orbital approach

245th National Meeting (2013)

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