A Local Charge State Fixation Approach for Resolving Charge-Flow Problems in Reorganization Energy Calculations of...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Marcus theory describes charge transport, utilizing donor-bridge-acceptor (D-B-A) models.
• Constrained density functional theory (CDFT) is used for charge-localized states, but struggles with π-conjugated systems.
• Existing methods like partial geometry fixation and ONIOM are insufficient for accurate reorganization energy calculations.

Purpose of the Study:

• To develop a novel Local Charge State Fixation (LCSF) method for calculating reorganization energies in D-B-A dimers.
• To enable accurate charge-localized state calculations without explicit electronic density constraints.
• To provide a computationally efficient alternative to CDFT for post-Hartree-Fock (post-HF) methods.

Main Methods:

• Developed LCSF method optimizing charged monomers independently.
• Applied Eckart condition for aligning fragments of neutral and charged dimers.
• Grafted monomers to create charge-localized dimer geometries for reorganization energy evaluation.
• Validated LCSF using Hartree-Fock and MP2 calculations on various D-B-A systems and zinc oxo clusters.

Main Results:

• LCSF yielded comparable reorganization energies to CDFT for 1,4-diphenylbutane (PS).
• LCSF provided larger reorganization energies for trans,trans-1,4-diphenyl-1,3-butadiene (PD) and 1,4-diphenylbutadiyne (PT), indicating reduced electron delocalization.
• Demonstrated applicability for electron transfer rate calculations in zinc oxo cluster dimers.

Conclusions:

• LCSF is a computationally efficient strategy for reorganization energy calculations in dimer systems.
• The method overcomes limitations of CDFT in π-conjugated systems.
• LCSF facilitates accurate charge transport studies, especially within post-HF frameworks.