The DQ and DQΦ electronic structure diabatization methods: Validation for general applications

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Adiabatic electronic states require transformation to diabatic states for accurate molecular dynamics simulations.
• The dipole-quadrupole (DQ) method was previously proposed for this transformation using dipole and quadrupole operators.

Purpose of the Study:

• To extend the DQ method by including the electrostatic potential, creating the DQΦ method.
• To test and illustrate the robustness of the DQ and DQΦ methods for generating smooth diabatic potential energy curves.
• To demonstrate the generality of these methods across various molecular systems and chemical reactions.

Main Methods:

• The dipole-quadrupole-electrostatic-potential (DQΦ) diabatization method was developed.
• The method was applied to multi-state diabatizations of LiH and HCl, (H2)2, O3, and the Li + HF reaction.
• The dependence of the DQ method on the quadrupole moment weighting parameter was investigated.

Main Results:

• The DQΦ method provides improved diabatic potential energy curves, smoothly handling crossings and avoided crossings.
• The DQ method showed minimal dependence on the quadrupole parameter when sufficient states were included.
• The electrostatic potential addition improved diabatic potentials in several tested cases, enhancing method generality.

Conclusions:

• The DQΦ method is a robust and general approach for transforming adiabatic to diabatic states.
• The inclusion of electrostatic potential offers additional flexibility and improves diabatization accuracy.
• The developed methods are applicable to a wide range of chemical systems, including reactions.