Multicomponent density functional theory: Including the density gradient in the electron-proton correlation...

Area of Science:

• Quantum Chemistry
• Computational Physics
• Materials Science

Background:

• Multicomponent density functional theory (DFT) offers advantages for including nuclear quantum effects.
• The nuclear-electronic orbital (NEO) framework treats nuclei and electrons quantum mechanically.
• Previous functionals (epc17, epc18) improved accuracy but lacked simultaneous precision in densities and energies.

Purpose of the Study:

• To develop a novel electron-proton correlation functional for enhanced accuracy in quantum chemistry.
• To simultaneously achieve accurate proton densities and energies within the NEO-DFT framework.
• To investigate the impact of nuclear quantum effects on molecular geometries.

Main Methods:

• Derivation and implementation of a generalized gradient approximation (GGA) functional, epc19.
• Dependence of epc19 on electron and proton density gradients and densities.
• Application of the NEO-DFT/epc19 method to hydrogen and deuterium systems.

Main Results:

• The epc19 functional accurately predicts both proton densities and energies simultaneously.
• It reproduces the influence of nuclear quantum effects on optimized molecular geometries.
• NEO-DFT/epc19 provides accurate results for both hydrogen and deuterium without further parameterization.

Conclusions:

• The epc19 functional effectively captures key aspects of electron-proton correlation, highlighting the importance of gradient terms.
• This advancement enables more comprehensive studies of nuclear quantum effects and isotope effects.
• The developed method opens new avenues for exploring diverse chemical and physical systems.