A multiconfiguration pair-density functional theory-based approach to molecular junctions.

Area of Science:

• Computational Chemistry
• Condensed Matter Physics
• Molecular Electronics

Background:

• Single-molecule electronics offer unique properties but are challenging to model theoretically.
• Accurate modeling requires accounting for electron correlation, which is computationally intensive.
• Existing methods often struggle to efficiently capture both static and dynamic electron correlation.

Purpose of the Study:

• To develop and validate a novel computational approach for single-molecule electronic systems.
• To efficiently include static and dynamic electron correlation effects in theoretical models.
• To investigate the impact of active space selection on calculated electronic properties.

Main Methods:

• Combined the non-equilibrium Green's function (NEGF) formalism with multiconfiguration pair-density functional theory (MCPDFT).
• Utilized complete active space self-consistent field (CASSCF) wave functions as references.
• Performed conductance and transmission calculations on alkane and benzyne molecular junctions.

Main Results:

• The NEGF-MCPDFT method efficiently incorporates both static and dynamic electron correlation.
• For alkane junctions (dominated by dynamic correlation), results align with standard DFT-NEGF.
• For benzyne junctions (significant static correlation), NEGF-MCPDFT shows distinct results, capturing effects beyond standard DFT.

Conclusions:

• NEGF-MCPDFT provides a more accurate description of electronic structure in single-molecule junctions with significant electron correlation.
• The method offers a computationally feasible way to study complex electronic phenomena in molecular systems.
• Active space selection is crucial for accurate results in MCPDFT calculations.