A direct diabatic states construction method with consistent orbitals for valence and Rydberg states.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Accurate calculation of diabatic states and couplings is crucial for understanding chemical reaction dynamics.
• Existing methods often face challenges in directly constructing diabatic states and their couplings, especially for complex systems.

Purpose of the Study:

• To introduce a novel methodology, Direct Diabatic States Construction (DDSC), for the direct and efficient construction of diabatic states.
• To enable the direct computation of diabatic couplings and non-adiabatic coupling vectors.

Main Methods:

• DDSC integrates fragment wavefunctions into an anti-symmetric total wavefunction.
• It utilizes fragment-localized state-consistent molecular orbitals for direct diabatic state construction.
• Diabatic states are formed as linear combinations of diabatic configurations.

Main Results:

• The DDSC method was successfully applied to LiH and (C2H4)2+ molecules.
• It demonstrated effectiveness in constructing both valence and Rydberg diabatic states.
• Direct computation of diabatic couplings and their conversion to non-adiabatic coupling vectors was achieved.

Conclusions:

• DDSC provides an efficient approach for building diabatic potential energy matrices.
• The method is particularly suitable for systems with clear fragment partitions and weak inter-fragment interactions, such as charge transfer reactions.
• DDSC offers a robust tool for studying complex chemical dynamics.