Global Hybrid Multiconfiguration Pair-Density Functional Theory.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Strongly correlated systems pose significant challenges for traditional electronic structure methods.
• Accurate modeling requires capturing both static and dynamical electron correlation effects.
• Existing methods often face limitations in computational cost or accuracy for these systems.

Purpose of the Study:

• To develop a novel, computationally efficient hybrid method for describing strongly correlated systems.
• To combine the strengths of multiconfiguration pair-density functional theory (MC-PDFT) with variational two-electron reduced-density matrix (v2RDM) theory.
• To enable accurate calculations of static and dynamical correlation effects.

Main Methods:

• A global hybrid extension of MC-PDFT, termed λ-MC-PDFT, is introduced.
• A linear decomposition of the electron-electron repulsion term combines nonlocal exchange (from v2RDM-driven CASSCF) with local exchange (from on-top pair-density functional).
• The method utilizes a variational two-electron reduced-density matrix (v2RDM) approach within complete active-space self-consistent field (CASSCF) theory, ensuring polynomial scaling.

Main Results:

• The λ-MC-PDFT scheme inherits the simplicity and symmetry resolution benefits of MC-PDFT.
• The method demonstrates polynomial scaling computational effort when combined with v2RDM-CASSCF.
• Accurate descriptions of challenging multiconfigurational problems were achieved, including N2 dissociation, H2O double dissociation, and ozone cycloadditions.

Conclusions:

• λ-MC-PDFT provides an efficient and accurate approach for studying strongly correlated systems.
• The method successfully models static and dynamical correlation effects.
• This development offers a powerful tool for investigating complex chemical phenomena.