Embedded density functional theory for covalently bonded and strongly interacting subsystems.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Embedded density functional theory (e-DFT) is crucial for modeling complex molecular systems.
• Accurately describing the electronic structure of strongly interacting subsystems remains a challenge.
• The nonadditive kinetic potential (NAKP) significantly impacts e-DFT calculations.

Purpose of the Study:

• To present a general implementation of the Exact Embedding (EE) method for e-DFT.
• To accurately calculate the nonadditive kinetic potential (NAKP) contributions.
• To assess the performance of the EE method against approximate kinetic energy functionals.

Main Methods:

• Implementation of the Exact Embedding (EE) method within e-DFT.
• Calculation of potential energy curves for molecular dissociation (Li(+)-Be, CH(3)-CF(3), water clusters).
• Comparison of EE method results with Kohn-Sham calculations and approximate functionals.
• Development and application of a pairwise approximation for NAKP.

Main Results:

• The EE method shows excellent agreement with reference Kohn-Sham calculations.
• Approximate kinetic energy functionals lead to qualitative failures in energies and structures.
• A pairwise approximation to NAKP enables efficient parallelization.
• Benchmark calculations on molecular crystals demonstrate ideal, size-independent scaling.

Conclusions:

• The Exact Embedding method provides a robust and accurate approach for e-DFT.
• The developed pairwise NAKP approximation facilitates efficient calculations for large systems.
• This work advances the reliable computational study of strongly interacting molecular subsystems.