Range separated hybrids of pair coupled cluster doubles and density functionals.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Materials Science

Background:

• Coupled cluster methods are accurate but computationally expensive.
• Pair Coupled Cluster Doubles (pCCD) offers a cost-effective simplification, capturing static correlation.
• Incorporating dynamic correlation into pCCD remains a challenge.

Purpose of the Study:

• To develop a hybrid method combining pCCD with Density Functional Theory (DFT).
• To efficiently incorporate dynamic correlation into the pCCD framework.
• To maintain the low cost and symmetry-preserving advantages of pCCD.

Main Methods:

• Combining pCCD with Kohn-Sham functionals.
• Splitting the Coulomb operator into short- and long-range components.
• Evaluating electron correlation using pCCD for long-range and DFT for short-range interactions.
• Eliminating double counting and suppressing self-interaction errors.

Main Results:

• The developed pCCD+DFT hybrid method successfully incorporates dynamic correlation.
• The approach maintains the size-consistency and low cost of pCCD.
• Calculations on benchmark systems show significant improvement over pure pCCD where both correlation types are crucial.

Conclusions:

• The pCCD+DFT hybrid method is a promising approach for accurate and efficient electronic structure calculations.
• This method provides a balanced treatment of static and dynamic electron correlation.
• It offers a viable alternative for studying complex chemical systems where both correlation types are important.