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Re^3: Excited-state geometry optimization with numerical gradients

Alex Granovsky

Dear Dawid,

indeed, the use of $numgrd input group is the most common and
preferred way to specify state of interest for numerical gradient
computations, which works even for computation types/input groups
that do not support istate input.

The istate keyword in $mcscf and some other groups is not useless
however. It indicates the state of interest, e.e. the state for which
properties or gradient should be computed, or one of the states for
which ConInt optimization should be performed, etc. For example,
it is very helpful to have istate in $mcscf and in $numgrd groups
because this allows computation and direct comparison of semi-
numerical and numerical MCSCF gradients.

Hope this helps.

Kind regards,
Alex Granovsky

On Wed Jan 4 '17 11:21pm, Dawid wrote
>Dear Professor Granovsky,

>Thank you for clarifying that. I got confused after reading the
>manual which says that

>"Then, three other important keywords should be mentioned. The NGRADS keyword can be used
>to request gradients for multiple states of interest, when using a method that can calculate the
>energies of several states at once (such as MCSCF). The default is NGRADS=1, meaning that the
>gradient is only computed for the lowest energy state. NGRADS=3, for example, will calculate the
>gradients of the three lowest states. Obviously, the amount of states requested with NGRADS
>should not be larger than the amount of states available."

>as well as for ISTATE

>"This option selects the target state of interest, i.e. the state which’ gradient is to
>be used by other parts of the program, for example during geometry optimization
>involving numerical gradients. This option is intended for use together with the
>NGRADS option. For instance, to optimize the second root of TDDFT or XMCQDPT,
>set NGRADS equal to or greater than 2, set ISTATE to 2, and properly set other
>relevant parameters controlling the number of computed roots during TDDFT or
>XMCQDPT procedure to capture at least two states. (Default is 1)

>So I figured out that even though I use ISTATE in $XMCQDPT I
>still need it properly set in $NUMGRD.

>Best regards,
>Dawid Grabarek

>On Wed Jan 4 '17 10:42pm, Alex Granovsky wrote
>>Dear Dawid,


 $XMCQDPT2 istate=2 $END 

>>is the valid way to specify that you requests optimization of a second root.
>>This can be done differently (using $numgrd input) but this is not necessary.

>>Kind regards,
>>Alex Granovsky
>>On Wed Jan 4 '17 8:26pm, Dawid wrote
>>>Dear All,

>>>What does actually happen if I specify XMC-QDPT2 geometry optimization
>>>calculations in the first excited state (istate=2) with 2-SA-CASSCF
>>>reference but I don't use

>>> ngrads=2
>>> istate=2

>>>Does it mean that the geometry in the first excited state is
>>>calculated based on the ground electronic state gradient?

>>>Best regards,

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