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Re^4: Excited state CASSCF dipole moments

Alex Granovsky
gran@classic.chem.msu.su


Dear Matthieu,

I have attached archive with a sample input file.

Basically, the trick is in addition to SA-MCSCF to request CI
of exactly the same type and use $gugdm group to select the
state of interest.

Hope this helps.

Kind regards,
Alex





On Tue Apr 2 '13 3:52am, Alex Granovsky wrote
---------------------------------------------
>Dear Matthieu,

>Sorry for delay with my reply.

>As to relaxed vs. expectation value dipole moments,
>the first are defined as the derivatives of a total energy
>with respect to the strength of an external electric field.
>The second are defined as the expectation value of the dipole
>operator computed using calculated wavefunction.

>These tho are the same only for fully variational methods
>like e.g. RHF or single-state MCSCF. Otherwise, they differ.  
>Moreover, there as some methods for which expectation value-type
>properties cannot be defined at all. Most people believes that
>response-type properties are preferred even if both types are
>available (e.g., for CI).

>To compute numerical polarizabilities using finite differences,
>you need to use response-type dipole moments.

>I'll split my answer to your post into several parts.

>I'll attach the sample input you are asking for to my next post.

>As to transition moments, this may require some more time to
>be answered. I will answer this when I will have some ideas
>or news on this. Meanwhile, I'd welcome any additional input
>from your side.

>Kind regards,
>Alex
>
>
>On Thu Mar 28 '13 1:07pm, Matthieu Sala wrote
>---------------------------------------------
>>On Thu Mar 28 '13 2:50am, Alex Granovsky wrote
>>----------------------------------------------

>>Dear Alex,

>>Thank you for answering this fast.

>>From what you say, I understand that relaxed dipole moments are more accurate than expectation-value ones. Is that correct ?

>>However, as I said I am interested in excited state polarizability for which I don't expect to get very accurate results from CASSCF.
>>Indeed we have compared CASSCF (with molpro), zero-order QDPT, MRCI (with molpro) and XMCQDPT2 (by double energy differentiation) and found that dynamic correlation is important.

>>Therefore expectation-value dipole would be sufficient four our purpose and an input example would be of great help.

>>I attach an input file for pyrazine which we are studying. It has zero dipole moments but we are interested in a field induced dipole so it is a RUNTYP=FFIELD input. I know that I don't use the fastest options for CASSCF and XMCQDPT2 but I like the fullnr and guga combination because it converges well and in this case it remains quite fast.

>>I would like to add a comment on zero-order QDPT transition moments.

>>In a previous post I was concern with the ZO-QDPT TDMs for aniline, I found that when the XMCQDPT2 model space contains only the states included in the SA-CASSCF part then I obtained good ZO-QDPT TDMs (the same as the CASSCF ones). However when the model space size was increased to include important contributions from higher states then the TDM for the 2nd pipi* excited state was very bad. You sent me a corrected input that did not change the problem (although it was useful for me as an example for good XMCQDPT2 calculations.)

>>I find the same behaviour in pyrazine. When increasing the size of the model space the TDM for the third excited state (first pipi*) again become very bad.

>>I just wanted to bring this to your attention.

>>Thank you for your help and comments.
>>Best regards.

>>Matthieu
>>
>>
>>>Dear Matthieu,

>>>Do you need relaxed or expectation-value dipole moments?

>>>Relaxed dipole moments could be computed using the same
>>>approach as the one used by SA-CASSCF gradient code, namely,
>>>by differentiation of state-averaged dipole moment
>>>with respect to a state weight. This is because the differentiation
>>>of averaged one and two particle density matrices with respect to
>>>a state weight produces response-type state-specific density
>>>matrices. This is the most general and powerful statement related
>>>to such a differentiation which allows computation of state-specific
>>>gradients and any one and two-electron properties using such
>>>differentiation.

>>>If you can wait a month or so, the code for relaxed dipole moments
>>>will be available as a part of Firefly.

>>>Computation of expectation-value state-specific dipole moments is
>>>even simpler. The dipole moments of this type can be computed
>>>by the present code. If this is the type of dipole moments you need,
>>>please let me know and I'll post sample input file.

>>>Kind regards,
>>>Alex Granovsky
>>>
>>>
>>>On Wed Mar 27 '13 7:05pm, Matthieu Sala wrote
>>>---------------------------------------------
>>>>Dear Firefly users,

>>>>I would like to know if there is a way to compute excited state dipole moments from a state averaged CASSCF calculation in Firefly.

>>>>The reason is that I would like to compute excited state polarizabilities by finite differentiation of the dipole rather than double differentiation of the energy with respect to an applied field.

>>>>I know that I can obtain zero order QDPT dipole moments from a XMCQDPT2 calculation and that these might be better than CASSCF although not of full XMCQDPT2 quality. However I would like to compute pure CASSCF dipole moments, at least for the purpose of comparison.

>>>>Best regards.
>>>>Matthieu Sala

This message contains the 94 kb attachment
[ pyr_ffield_ci.rar ] A sample of expectation value-type state-specific properties for state-averaged CASSCF


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