Adventures in DFT by a wavefunction theorist.

Area of Science:

• Quantum Chemistry
• Computational Physics
• Electronic Structure Theory

Background:

• Density Functional Theory (DFT) is computationally efficient for electronic structure calculations due to its effective one-particle approach.
• However, DFT lacks a systematic way to improve its functionals, leading to thousands of variations without clear convergence.
• Ab initio methods like coupled-cluster (CC) theory offer rigorous convergence but are computationally demanding.

Purpose of the Study:

• To bridge the gap between computationally tractable DFT and rigorous ab initio methods.
• To explore a route for systematically improving Kohn-Sham DFT (KS-DFT) by leveraging the formal properties of CC theory.
• To address fundamental issues in KS-DFT, including the one-particle spectrum, self-interaction error, and the integer discontinuity.

Main Methods:

• The study proposes a theoretical perspective, not a specific computational method.
• It focuses on utilizing the exact formal properties of coupled-cluster (CC) theory.
• The aim is to connect CC theory to an effective one-particle formulation.

Main Results:

• The proposed approach aims to resolve the 'devil's triangle' of KS-DFT problems.
• This includes issues with the one-particle spectrum, self-interaction, and the integer discontinuity.
• The perspective suggests a path towards more accurate and systematically improvable electronic structure calculations.

Conclusions:

• Linking CC theory to an effective one-particle form offers a promising direction for advancing electronic structure calculations.
• This approach could lead to more reliable and systematically improvable DFT functionals.
• Addressing the core limitations of KS-DFT is crucial for accurate predictions in chemistry and physics.