A Dynamically Weighted Constrained Complete Active Space Ansatz for Constructing Multiple Potential Energy Surfaces...

Area of Science:

• Computational Chemistry
• Surface Science
• Quantum Mechanics

Background:

• Simulating molecules on metal surfaces is crucial for understanding heterogeneous catalysis and electrochemistry.
• Accurate electronic structure calculations are needed to model interactions between molecules and metal surfaces.
• Existing methods face challenges in describing the electronic continuum near metals.

Purpose of the Study:

• To develop and implement a novel computational approach for describing molecules on metal surfaces.
• To improve the accuracy and robustness of electronic structure calculations in such systems.
• To enable more reliable simulations of electron transfer and electrochemical dynamics.

Main Methods:

• Derivation and implementation of equations for a dynamically weighted, state-averaged constrained CASSCF(2,2) wave function.
• Constraining the overlap between active orbitals and impurity atomic orbitals.
• Calculation of system-bath electronic couplings considering the metal's electronic continuum.

Main Results:

• Demonstration that a partial orbital overlap constraint is more robust than a full constraint.
• Successful calculation of electronic couplings for molecules near metal surfaces.
• Development of a computationally tractable method for complex surface interactions.

Conclusions:

• The developed constrained CASSCF method provides a robust framework for electronic structure calculations of molecules on metal surfaces.
• This approach enhances the simulation of heterogeneous electron transfer and electrochemical processes.
• The method is expected to be highly valuable for future research in surface chemistry and electrochemistry.