Subsystem density functional theory with meta-generalized gradient approximation exchange-correlation functionals.

Area of Science:

• Computational chemistry
• Quantum chemistry
• Theoretical chemistry

Background:

• Subsystem density functional theory (DFT) is a powerful method for studying large molecular systems.
• Meta-generalized gradient approximation (meta-GGA) exchange-correlation functionals offer improved accuracy but are challenging to implement in subsystem DFT.
• Current methods face limitations due to the dependence of meta-GGA functionals on the Kohn-Sham kinetic energy density (KED), which is not an explicit functional of the electron density.

Purpose of the Study:

• To propose and validate a novel approximation for incorporating meta-GGA functionals into subsystem DFT calculations.
• To overcome the limitations of applying KED-dependent functionals in subsystem DFT.
• To assess the accuracy and performance of the proposed method for non-bonded molecular systems.

Main Methods:

• A Laplacian-level approximation for the Kohn-Sham kinetic energy density (KED) was developed.
• This approximation enables the direct application of meta-GGA exchange-correlation functionals within the subsystem DFT framework.
• The methodology was tested on non-bonded molecular systems, comparing results with supermolecular calculations.

Main Results:

• The proposed Laplacian-level approximation provides a simple and accurate way to implement meta-GGA functionals in subsystem DFT.
• Density and energy errors obtained using this method are comparable to conventional approaches.
• The accuracy is primarily governed by approximations in the non-additive kinetic embedding term, as confirmed by error decomposition analysis.

Conclusions:

• The developed method effectively extends the applicability of high-accuracy meta-GGA functionals to subsystem DFT.
• This advancement facilitates more precise computational studies of complex molecular systems using subsystem DFT.
• The approach offers a robust and efficient alternative for electronic structure calculations in computational chemistry.