Multicomponent density functional theory study of the interplay between electron-electron and electron-proton correlation
Abstract
The interplay between electron-electron and electron-proton correlation is investigated within the framework of the nuclear-electronic orbital density functional theory (NEO-DFT) approach, which treats electrons and select protons quantum mechanically on the same level. Recently two electron-proton correlation functionals were developed from the electron-proton pair densities obtained from explicitly correlated wavefunctions. In these previous derivations, the kinetic energy contribution arising from electron-proton correlation was neglected. In this paper, an electron-proton correlation functional that includes this kinetic energy contribution is derived using the adiabatic connection formula in multicomponent DFT. The performance of the NEO-DFT approach using all three electron-proton correlation functionals in conjunction with three well-established electronic exchange-correlation functionals is assessed. NEO-DFT calculations with these electron-proton correlation functionals capture the increase in the hydrogen vibrational stretching frequencies arising from the inclusion of electron-electron correlation in model systems. Electron-proton and electron-electron correlation are found to be uncoupled and predominantly additive effects to the total energy for the model systems studied. Thus, electron-proton correlation functionals and electronic exchange-correlation functionals can be developed independently and subsequently combined together without re-parameterization.
- Publication:
-
Journal of Chemical Physics
- Pub Date:
- May 2012
- DOI:
- 10.1063/1.4709609
- Bibcode:
- 2012JChPh.136q4114S
- Keywords:
-
- density functional theory;
- electron correlations;
- exchange interactions (electron);
- hydrogen;
- vibrational states;
- 31.15.eg;
- 31.15.vj;
- 33.15.Mt;
- 33.20.Tp;
- Exchange-correlation functionals;
- Electron correlation calculations for atoms and ions: excited states;
- Rotation vibration and vibration-rotation constants;
- Vibrational analysis