Nuclear quantum effects such as zero point energy, nuclear delocalization, and tunneling play an important role in a wide range of chemical processes. The nuclear-electronic orbital (NEO) approach treats specified nuclei, typically protons, quantum mechanically on the same level as the electrons with multicomponent density functional theory (DFT) or wave function methods. Electron-proton correlation functionals have been developed to address the significant challenge within NEO-DFT of producing accurate proton densities and energies. Moreover, time-dependent DFT and related methods within the NEO framework have been developed for the calculation of electronic, proton vibrational, and electron-proton vibronic excitations. An effective strategy for calculating the vibrational frequencies of the entire molecule within the NEO framework has also been devised and has been shown to incorporate the most significant anharmonic effects. Furthermore, multicomponent wave function methods based on coupled cluster, configuration interaction, and orbital-optimized perturbation theory approaches, as well as multicomponent equation-of-motion coupled cluster methods for computing excited electronic and proton vibrational states, have been developed within the NEO framework. Multistate DFT methods within the NEO framework enable the calculation of tunneling splittings and vibronic couplings relevant to proton transfer and proton-coupled electron transfer reactions. Recently, real-time NEO methods have been developed and used to study nonequilibrium dynamical processes such as photoinduced proton transfer. These combined NEO methods enable the inclusion of nuclear quantum effects and non-Born-Oppenheimer effects in calculations of proton affinities, optimized geometries, vibrational frequencies, isotope effects, minimum energy paths, excitation energies, tunneling splittings, vibronic couplings, and nonequilibrium dynamics for a wide range of chemical applications.
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References
S. P. Webb, T. Iordanov, and S. Hammes-Schiffer, Multiconfigurational nuclear-electronic orbital approach: Incorporation of nuclear quantum effects in electronic structure calculations, J. Chem. Phys. 117, 4106-4118 (2002).
F. Pavošević, T. Culpitt, and S. Hammes-Schiffer, Multicomponent quantum chemistry: Integrating electronic and nuclear quantum effects via the nuclear-electronic orbital method, Chem. Rev.120, 4222-4253 (2020).
L. Zhao, Z. Tao, F. Pavošević, A. Wildman, S. Hammes-Schiffer, and X. Li, Real-time time-dependent nuclear-electronic orbital approach: Dynamics beyond the Born-Oppenheimer approximation, J. Phys. Chem. Lett. 11, 4052-4058 (2020).
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Financial Support
The Cooper Union for the Advancement of Science and Art is pleased to provide support for the 2024 VWSCC through a generous donation from Alan Fortier.
We thank Leibniz Institute for Catalysis (LIKAT) and CECAM for their support.
Virtual Winter School on Computational Chemistry