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Alex Granovsky
gran@classic.chem.msu.su

The default for XMCQDPT2/XMCQDPT2 is to pick up the totally
symmetric irrep. You can change this using istsym keyword.
The mapping table is as follows:

                         istsym 

group        1   2  3    4   5    6   7   8
C1           A
Ci           Ag  Au
Cs           A'  A''
C2           A   B
C2v          A1  A2  B1  B2
C2h          Ag  Bg  Au  Bu
D2           A   B1  B2  B3
D2h          Ag  B1g B2g B3g  Au  B1u B2u B3u

Hope this helps.

All the best,
Alex




On Thu Oct 3 '13 7:33pm, lello wrote
------------------------------------
>Dear Alex,

>I am a bit confused. What happens if I use ISTSYM=2
>in an MCSCF calculation and, in the same run I
>do an MCQDPT2? Which states are selcted for MP2?

>Lello

>On Thu Oct 3 '13 3:14pm, Alex Granovsky wrote
>---------------------------------------------
>>Dear Lello,
>>Dear Thom,

>>Thom is right that the described convention is used by all CI codes
>>which work in AO basis. At present, this are exactly CIS/TDHF/TDDFT.

>>The convention for GUGA/ALDET CI is different. In addition,
>>XMCQDPT/MCQDPT code applies yet another convention.

>>Kind regards,
>>Alex Granovsky
>>
>>
>>
>>On Thu Oct 3 '13 12:25pm, Thomas Pijper wrote
>>---------------------------------------------
>>>Dear Lello,

>>>AFAIK, the information in the manual is correct. My guess is that different parts of the Firefly code number the irreps differently. The numbering on page 121 pertains to the TDHF/TDDFT/CIS code, while the second numbering you refer to (ISTSYM=4 for Bu in C2h) pertains to the (X)MCQDPT2 code. Perhaps Alex can provide more information (or correct me if I'm wrong).

>>>Page numbers will be added in the next update.
>>>
>>>
>>>Kind regards,
>>>Thom
>>>
>>>
>>>
>>>
>>>On Thu Oct 3 '13 11:07am, lello wrote
>>>-------------------------------------
>>>>Dear All,

>>>>concerning the manual I have found some contradictory information
>>>>about the use of symmetry with ISTSYM.

>>>>The manual (on page 121) states that the number ISTSYM associated with the symmetry label can be found looking at the string
>>>>"DIMENSIONS OF THE SYMMETRY SUBSPACES"

>>>>The example gives ISTSYM=3 for the Bu label in C2h group.
>>>>Later in the manual one finds that ISTSYM=4 for Bu in C2h.
>>>>The main problem is that I am performing a CASSCF in C2h symmetry
>>>>and I must use ISTSYM=2 to get Bu states.

>>>>Am I doing something wrong or is there some error in the manual?

>>>>Also, is it possible to add page number to the manual?

>>>>Thanks,
>>>>Lello

>>>>On Wed Oct 2 '13 3:46pm, Thomas Pijper wrote
>>>>--------------------------------------------
>>>>>Dear all,

>>>>>The Firefly manual has been updated today. The new files can be found in the "Manuals" section.
>>>>>
>>>>>
>>>>>Kind regards,
>>>>>Thom