A Simple, Exact Density-Functional-Theory Embedding Scheme.

Area of Science:

• Quantum chemistry
• Computational physics
• Materials science

Background:

• Density functional theory (DFT) offers a formally exact framework for quantum embedding.
• Optimized effective potential (OEP) methods have been used to develop DFT-in-DFT methods equivalent to Kohn-Sham (KS) theory.
• Nonadditive kinetic energy contributions present challenges in quantum embedding.

Purpose of the Study:

• To present a significant simplification of quantum embedding methods.
• To introduce embedding schemes that avoid computationally demanding OEP calculations.
• To demonstrate the application of novel embedding techniques.

Main Methods:

• Utilizing Kohn-Sham (KS) theory as a simplification over OEP methods.
• Developing embedding schemes that enforce Pauli exclusion via a projection technique.
• Applying DFT-in-DFT, wave-function-in-DFT, and wave-function-in-Hartree-Fock embedding.

Main Results:

• Demonstrated a considerable simplification by directly applying KS theory.
• Successfully avoided numerically demanding OEP calculations through projection techniques.
• Presented illustrative applications of various embedding schemes.

Conclusions:

• The proposed projection technique effectively enforces Pauli exclusion in quantum embedding.
• Simplified embedding schemes offer efficient and accurate alternatives to OEP-based methods.
• These advancements facilitate broader applications of DFT embedding in complex systems.