A Comparison of Exact and Model Exchange-Correlation Potentials for Molecules

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Materials Science

Background:

• Density Functional Theory (DFT) relies on approximations for exchange-correlation (XC) potentials.
• Accurate XC potentials are crucial for reliable DFT calculations.
• The inverse DFT problem offers a route to obtain exact XC potentials for benchmarking.

Purpose of the Study:

• To compute the exact XC potential for seven molecular systems.
• To compare the exact XC potential with various model XC potentials.
• To assess the accuracy of current DFT approximations.

Main Methods:

• Full configuration interaction (FCI) calculations were used to obtain reference densities.
• The inverse DFT problem was solved to derive exact XC potentials.
• Model XC potentials from nonlocal and semilocal/local functionals were evaluated.

Main Results:

• Exact XC potentials were computed for dihydrogen, lithium hydride, water, and ortho-benzyne.
• Model XC potentials exhibited significantly higher errors than the exact potentials.
• SCAN0 demonstrated the best agreement among the tested model XC functionals.

Conclusions:

• Tests against exact XC potentials are vital for improving DFT approximations.
• Satisfying exact conditions and incorporating nonlocal effects are key for accurate XC functionals.
• This study provides a new benchmark for developing more reliable DFT methods.