Coupled Cluster Method with Single and Double Excitations Tailored by Matrix Product State Wave Functions

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Strongly Correlated Systems

Background:

• The density matrix renormalization group (DMRG) is a leading method for strongly correlated molecular systems.
• However, DMRG is not suitable for accurately computing dynamic correlation effects.
• Existing methods struggle to balance nondynamic and dynamic correlation in complex molecules.

Purpose of the Study:

• To develop a novel computational method for accurately treating dynamic correlation in post-DMRG calculations.
• To combine the strengths of DMRG for nondynamic correlation with coupled cluster (CC) theory for dynamic correlation.
• To apply the new method to challenging multireference systems, including N2, Cr2, and oxo-Mn(Salen).

Main Methods:

• A "post-DMRG" approach integrating tailored coupled cluster (CC) theory.
• DMRG is used to describe nondynamic correlation.
• CC theory is employed to incorporate dynamic correlation effects.

Main Results:

• The novel method successfully treats dynamic correlation beyond DMRG.
• Accurate calculations were performed for N2 and Cr2 molecules.
• The first post-DMRG computations for oxo-Mn(Salen) were conducted, clarifying spin state energy ordering.

Conclusions:

• The combined DMRG-CC approach provides an accurate treatment for strongly correlated systems.
• This method overcomes limitations of DMRG in handling dynamic correlation.
• The study demonstrates the method's potential for complex molecular systems and electronic structure problems.