LR-TDDFT of excited state

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Dear all,
I am trying to calculate the absorption spectrum of excited CHBr3 with an extended C-Br bond. CHBr3 is in excited T2, where one HOMO-1 electron is excited to LUMO. I can use the following tag to do it, however, it doesn't necessarily converge to T2 state. Sometimes, it only converges to T1 state.

vectors swap beta 55 56

Is it possible to run a first LR-TDDFT calculation with tag CIVECS to export the T2 state and perform the second LR-TDDFT based on the CI vectors from the first step?

If we have to revise the code, what subroutines I should revise?

Thanks a lot!

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No, you cannot perform a second LR-TDDFT calculation with a reference built from the CI vectors of an excited state. LR-TDDFT is formulated for a single determinant reference state and your T2 solution from the first LR-TDDFT would be a linear combination of determinants.

Quadratic response TDDFT could give you the absorption spectrum for an excited state; however, it is not implemented in NWChem (the only implementation I am aware of is in the code Dalton).

Within NWChem, you could attempt our RT-TDDFT based approach to excited state absorption ("Excited state absorption from real-time time-dependent density functional theory" JCTC vol. 11 4294-4303 [2015] While not documented, the functionality for this approach is in version 6.8 of the code. You would need to first run a LR-TDDFT gradient calculation on the excited state of interest in order to generate the excited state density matrix (or matrices in the case of an open shell calculation). You can then use the excited state density as your starting point by adding the appropriate load command to your RT-TDDFT input block:

load density <file name>.dmat

for closed shell or

load density <file name>.dmatA <file name>.dmatB

for open shell, where you would obviously insert the file name for the density matrix (matrices) generated from the LR-TDDFT gradient calculation. From there you should be able to follow the method outlined in the above cited paper to generate the absorption spectrum.
Edited On 5:52:34 AM PST - Fri, Dec 7th 2018 by Sean

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Posts 1 my case i was trying to do excited state geometry optimization using the analytical gradient of LR-TDDFT. I did not find the relevant part of the manual that describes the gradient calculation of LR-TDDFT. so, I am wondering if this function available in dalton? if yes, how to use it? Thank you for your help!
Edited On 4:09:18 PM PST - Thu, Feb 28th 2019 by AvritSase

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Sorry I misunderstood you. Geometry optimization on the excited state is straightforward within NWChem. See the third example input in the documentation

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