A Regularized Second-Order Correlation Method from Green's Function Theory.

Area of Science:

• Quantum chemistry
• Condensed matter physics
• Computational materials science

Background:

• Electronic correlation is crucial for accurately describing molecular and material properties.
• Traditional methods like MP2 and CCSD struggle with strongly correlated systems, leading to unphysical divergences.
• Green's function theory provides a powerful framework for electronic structure calculations.

Purpose of the Study:

• To develop a scalable and accurate single-particle framework for treating electronic correlation.
• To introduce a novel perturbation theory that overcomes the limitations of existing methods in strongly correlated regimes.
• To provide an efficient and size-consistent method for electronic structure calculations.

Main Methods:

• Derivation of a size-extensive Brillouin-Wigner perturbation theory from single-particle Green's function.
• Introduction of the Goldstone self-energy to define Quasi-Particle MP2 (QPMP2) theory.
• Application and validation of QPMP2 on Hubbard dimer and larger Hubbard models.

Main Results:

• QPMP2 accurately reproduces the exact ground state energy and properties of the Hubbard dimer.
• The method qualitatively reproduces the metal-to-insulator transition in larger Hubbard models, unlike traditional methods.
• QPMP2 demonstrates efficient, size-consistent regularization of MP2 for strongly correlated molecular systems.

Conclusions:

• QPMP2 offers a robust and scalable solution for electronic correlation problems, particularly in strongly correlated systems.
• The developed framework provides a significant advancement over existing perturbation and coupled cluster theories.
• QPMP2 shows promise for accurate and efficient simulations of complex molecules and materials.