Communication: double-hybrid functionals from adiabatic-connection: the QIDH model.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Density functional theory (DFT) relies on accurate exchange-correlation (XC) functionals.
• Double-hybrid (DH) functionals offer improved accuracy by including a fraction of exact exchange and MP2-like correlation.
• Developing parameter-free DH functionals remains a significant challenge.

Purpose of the Study:

• To propose a new, parameter-free approach for deriving double-hybrid exchange-correlation functionals.
• To develop novel DH functionals based on the adiabatic-connection formalism.
• To assess the performance and self-interaction error of the new functionals.

Main Methods:

• The study employs the adiabatic-connection (AC) formalism.
• A quadratic model for the coupling parameter integrand is developed, satisfying known limiting conditions.
• Integration of the model yields DH functionals with a single parameter determined by MP2 correlation weight.
• Non-empirical PBE and TPSS functionals are incorporated.

Main Results:

• Two new parameter-free DH functionals are successfully derived.
• Extensive testing on the GMTKN30 benchmark suite was performed.
• The new functionals demonstrate performance competitive with state-of-the-art DHs.
• Significantly improved self-interaction error compared to existing DHs was observed.

Conclusions:

• The proposed AC-based approach provides a viable route to parameter-free DH functionals.
• The developed functionals offer a balance of accuracy and reduced self-interaction error.
• This work opens new avenues for designing accurate and reliable DH XC functionals.