Multicomponent density functional theory with density fitting.

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Materials Science

Background:

• Multicomponent Density Functional Theory (MDFT) enables the inclusion of nuclear quantum effects and simulation of diverse particles.
• Standard DFT implementations face challenges in achieving optimal efficiency.
• Developing efficient MDFT methods is crucial for accurate simulations of quantum systems.

Purpose of the Study:

• To introduce an efficient Multicomponent Density Functional Theory implementation using auxiliary DFT.
• To focus on molecular systems containing both electrons and quantum protons.
• To evaluate the performance of various electron-proton correlation functionals.

Main Methods:

• Implementation of MDFT within the auxiliary DFT framework in the deMon2k code.
• Utilizing a dual variational procedure to determine auxiliary electron and proton densities.
• Employing fitted densities for classical Coulomb interactions and exchange-correlation potentials, including electron-proton correlation (EPC).

Main Results:

• Auxiliary densities are suitable for classical Coulomb interactions and EPC, with considerations for the electronic auxiliary basis set flexibility.
• Testing of various EPC functionals on proton affinities demonstrated their applicability.
• The density fitting approach in MDFT provides significant computational advantages and scales well with system size.

Conclusions:

• The auxiliary DFT approach offers an efficient pathway for MDFT calculations involving electrons and quantum protons.
• Density fitting in MDFT significantly reduces computational cost while maintaining accuracy.
• This implementation facilitates more accessible and scalable simulations of quantum mechanical systems.