Nuclear-electronic orbital (NEO) method
We have developed the nuclear-electronic orbital (NEO) method for the incorporation of nuclear quantum effects into electronic structure calculations. In the NEO approach, specified nuclei are treated quantum mechanically on the same level as the electrons, and mixed nuclear-electronic wavefunctions are calculated variationally with molecular orbital methods. Both electronic and nuclear molecular orbitals are expanded in Gaussian basis sets, and the energy is minimized with respect to all molecular orbitals, as well as the centers of the nuclear basis functions. Correlation among electrons and nuclei can be included with multiconfigurational, explicitly correlated, perturbation theory, and density functional theory approaches. The advantages of the NEO approach are that nuclear quantum effects are incorporated during the electronic structure calculation, the Born-Oppenheimer separation of electrons and nuclei is avoided, nonadiabatic effects are included, excited vibrational-electronic states may be calculated, and its accuracy may be improved systematically.
For hydrogen transfer and hydrogen bonding systems, typically the hydrogen nuclei and all electrons are treated quantum mechanically. Electron-proton dynamical correlation is highly significant because of the attractive electrostatic interaction between the electron and the proton. We have formulated an explicitly correlated Hartree-Fock scheme to incorporate explicit electron-proton correlation directly into the variational self-consistent-field framework with Gaussian-type geminal functions. We have also formulated a multicomponent density functional theory and have developed electron-proton functionals based on the explicitly correlated electron-proton pair density. Initial applications illustrate that these new methods significantly improve the description of the nuclear densities, thereby leading to more accurate calculations of molecular properties such as geometries and frequencies. This approach also provides fundamental insight into the coupling between electronic and nuclear motions.
NEO methods developed or under development (in GAMESS)
Current NEO and NEO-related projects
Copyright (C) 2012 Sharon Hammes-Schiffer
Page last updated March 2, 2012