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Re: XMCQDPT2 wavefunction

Alex Granovsky
gran@classic.chem.msu.su


Dear Matthieu,

some comments on the execution flow of XMCQDPT2 computations
can be found here

http://classic.chem.msu.su/gran/gamess/xmcqdpt_intro.pdf

and in the updated Firefly v. 8.0.0 documentation:

http://classic.chem.msu.su/gran/gamess/docs.zip

In brief, XMCQDPT2 code typically performs canonicalization of MOs.
This requires some additional computations i.e. the extra CASCI-type
integral transformation, CASCI computations, first order state-
averaged density matrix construction, Fock matrix construction and
finally its block-diagonalization. The point is that XMCQDPT2 code
employs its own sets of CSFs and MOs. These MOs can be found in file
MCQD63, and the definition of CSFs can be found in file MCQD64.

What you asked for is the following part of the XMCQDPT2's output:

 *** EIGENVECTORS ***
 FIRST ORDER
 .............................................................
These are CASCI vectors 

 SECOND ORDER
 .................................................................. 
These are rotated CASCI vectors you are asking for for



At present, there is no way to force the use of the same CSFs
or determinants throughout all code.

Kind regards,
Alex Granovsky



On Sun Sep 22 '13 7:33pm, Matthieu Sala wrote
---------------------------------------------
>Dear Firefly users,

>I would like to know if there is a way to get the expansion coefficient of the XMCQDPT2 wavefunction in the basis of the CSF's of the underlying SA-CASSCF calculation.

>If I understand correctly, the expansion coeff. of the XMCQDPT2 wavefunction on the CASCI states are obtained in the EIGENVECTORS OF THE EFFECTIVE HAMILTONIAN section and the expansion coeff. of the CASCI states on the CSF's in the  -MCCI- BASED ON OPTIMIZED ORBITALS section.
>So by combining this information I can have what I'm looking for.

>However I want to have this information for each point along a potential scan and I found that the relative signs of the various coefficients are not consistent from one point to another.

>Is there a way to overcome this problem ?

>Best regards.
>Matthieu Sala
>


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