SOC for Diabatic-State-Based Methods

Questions
#1

Dear Community,

Is it possible to calculate spin-orbit coupling (SOC) between “diabatic states” obtained by one of the methods described in “10.15.2 Diabatic-State-Based Methods” of the manual 10.15.2 Diabatic-State-Based Methods‣ 10.15 Electronic Couplings for Electron- and Energy Transfer ‣ Chapter 10 Molecular Properties and Analysis ‣ Q-Chem 6.4 User’s Manual ?

#2

If this option is available then I am not aware of it. However, the diabatic method must give you the adiabatic-to-diabatic transformation coefficients and you should then be able to apply those to the SOCs. Some code to extract SOC parameters from Q-Chem to construct and diagonalize the Breit-Pauli Hamiltonian is described in the paper below and could probably be adapted for this purpose.

#3

Dear John,

Thank you very much for the prompt reply!
Do I understand you correctly that one would need to compute SOC between adiabatic states first?
If so, how to obtain these adiabatic states? And how to compute SOC between them using Q-Chem?
My problem is prototypical (ground-state) charge transfer from donor to acceptor, D−A⟶DA− (eq. 10.152 in the manual), but with SOC.

#4

In quantum chemistry you always need to compute adiabatic (i.e., Born-Oppenheimer) states first, even if some particular diabatization algorithm might hide this fact from you, because diabatic states have no unique definition - they are models. Please see the Q-Chem manual for diabatization I don’t know the particulars of the diabatization algorithm but it’s somehow using TDDFT adiabatic states, then transforming to a diabatic basis according to some well-defined procedure. For calculation of SOC, you can see the paper cited above.