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SF-ADC(3) analytical excited state gradient

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Author Post
Member
Registered: May 2018
Posts: 1
Hi everyone,

I’m going to study conical intersection (S0/S1) in a ring-opening reaction. To do so, I would like to do relaxed potential energy scan for ground and singlet excited states using “Spin-Flip ADC(3)” method which is implemented in Q-Chem program. I’ve figured out that its analytical gradient for the excited state is available (see: The Journal of Chemical Physics 145 , 084102 (2016)). I’ve found an example in the manual for calculating the vertical excitations. Now, I wonder how to specify the interesting (excited) state that I want to performe the optimization in the input file and is it possible to tell the program only calculate singlet excited stets like SF-TDDFT. Has anyone tried to do excited-state optimizations with SF-ADC(3) method using Q-Chem program?

Thank you so much


Best,

Mostafa
Administrator
Registered: Oct 2017
Posts: 17
I am not an expert in ADC, but I can give some general answers:
1) Since the original SF formulation of methods (CIS, TDDFT, EOM-CC, ADC) is not spin adapted, it is not possible to separate singlets and triplets at the moment of computation. Moreover, spin contamination is often the case, which should be taken with care.
2) For different methods the keywords are slightly different. For example, if you want to optimize and excited state in EOM-CC, you need to use CC_STATE_TO_OPT. Excited state optimization is also possible with TDDFT or CIS (check the manual for examples). I am not sure about ADC.
3) If there are issues with ADC gradients, you can use approximate paths from TDDFT and run ADC over the geometries in the path.

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