Multireference Perturbation Theory with Cholesky Decomposition for the Density Matrix Renormalization Group

Area of Science:

• Quantum chemistry
• Computational physics
• Materials science

Background:

• Accurate modeling of electron correlation is crucial for understanding molecular properties.
• Large molecular systems present significant computational challenges for traditional quantum chemistry methods.

Purpose of the Study:

• To introduce and validate a novel computational method, CD-DMRG-NEVPT2, for describing static and dynamic electron correlation.
• To apply this method to challenging problems in spin-state energetics, such as spin-crossover complexes.

Main Methods:

• Development of a second-order N-electron valence state perturbation theory (NEVPT2) utilizing a density matrix renormalization group (DMRG) reference wave function.
• Incorporation of Cholesky decomposition of two-electron repulsion integrals for computational efficiency (CD-DMRG-NEVPT2).
• Assessment of strongly and partially contracted variants of the method using a heme model.

Main Results:

• The CD-DMRG-NEVPT2 method efficiently describes static and dynamic correlation in large molecular systems.
• Demonstrated applicability to spin-state energetics of spin-crossover complexes with over 1000 atomic basis functions.
• Resolved a controversy regarding the spin ground state of a cobalt tropocoronand complex.

Conclusions:

• CD-DMRG-NEVPT2 offers a parameter-free, efficient, and accurate approach for multireference calculations on large systems.
• The method provides valuable insights into the electronic structure and spin properties of complex molecules.