Comparative performance of exchange and correlation density functionals in determining intermolecular interaction...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Accurate calculation of interaction potentials is crucial for understanding molecular behavior.
• Density functional theory (DFT) is a widely used method for electronic structure calculations.
• Weakly bound systems, like the methane dimer, present challenges for DFT due to the nature of van der Waals forces.

Purpose of the Study:

• To investigate the role of exchange and correlation functionals in DFT calculations of methane dimer interaction potentials.
• To evaluate the performance of 90 different density functionals, including hybrid functionals.
• To identify key factors influencing the accuracy of DFT for van der Waals interactions.

Main Methods:

• Utilized density functional theory (DFT) for electronic structure calculations.
• Employed 90 density functionals, comprising nine exchange and 10 correlation functional combinations.
• Focused on the minimum-energy D(3d) conformation of the methane dimer.

Main Results:

• Both exchange and correlation functionals critically influence the calculated interaction potentials.
• The performance of exchange functionals correlates with the reduced density gradient of their enhancement factor.
• Correlation energy is determined by the low-density behavior of the correlation enhancement factor.
• The correlation counterpart is as vital as the exchange functional for van der Waals interactions in the methane dimer.

Conclusions:

• The study highlights the equal importance of exchange and correlation functionals in DFT for van der Waals interactions.
• Findings provide insights into the seemingly unsystematic nature of DFT potentials for weakly bound systems.
• This work can guide the selection of DFT functionals for improved accuracy in studying non-covalent interactions.