Propagative block diagonalization diabatization of DFT/MRCI electronic states

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Calculating diabatic states is essential for studying non-adiabatic dynamics in molecular systems.
• Standard diabatization methods face limitations with the Density Functional Theory and Multireference Configuration Interaction (DFT/MRCI) approach due to specific restrictions.
• These restrictions include the absence of analytical derivative couplings and the inability to utilize non-canonical Kohn-Sham orbitals.

Purpose of the Study:

• To develop a robust framework for calculating diabatic states within the DFT/MRCI method.
• To overcome the limitations of existing diabatization strategies when applied to DFT/MRCI calculations.
• To enable accurate modeling of non-adiabatic effects in complex chemical systems.

Main Methods:

• A novel framework combining Density Functional Theory and Multireference Configuration Interaction (DFT/MRCI) was developed.
• A propagative variant of the block diagonalization diabatization method (P-BDD) was employed to calculate diabatic wavefunctions and potentials.
• The P-BDD method was adapted to circumvent the limitations of the standard DFT/MRCI formulation.

Main Results:

• The study successfully calculated diabatic potentials for the Lithium Hydride (LiH) molecule.
• The vibronic spectrum of Pyrazine was simulated, demonstrating the method's applicability.
• The combined DFT/MRCI and P-BDD approach accurately captured non-adiabatic coupling effects in both test cases.

Conclusions:

• The developed DFT/MRCI and P-BDD framework provides a reliable method for calculating diabatic states.
• This approach effectively addresses the challenges posed by the current DFT/MRCI formulation.
• The validated method offers a significant advancement for theoretical studies involving non-adiabatic dynamics.