Sent to CCL by: "Walid M. I. Hassan" [walid_m76|-|yahoo.com]
Dear Scientists
long time since I send email via this list,
my question is very simple does anyone know a software to determine the
avoided crossing or conical intersection between singlet and triplet states,
i mean states of different multiplicity
In Gaussian 09 manual, in Opt keyword ,under conical option it is written,
"Search for a conical intersection or avoided crossing using the state-
averaged CASSCF method. Avoided is a synonym for Conical. Note that
CASSCF=SlaterDet is needed in order to locate a conical intersection between
a singlet state and a triplet state."
I tried this and find it is impossible since in input file you determine a
singlet or triplet multiplicity but not both
and SlaterDet option just reverse the spin but do not change multiplicity
see this part of output to see the configurations
when I use singlet state with No SLATER DETERMINANT
I get the following configuration
Configuration 1 Symmetry 1 111000
Configuration 2 Symmetry 1 11ab00
Configuration 3 Symmetry 1 110100
Configuration 4 Symmetry 1 1a1b00
which become as follows with SLATER DETERMINANT
Configuration 1 Symmetry 1 111000
Configuration 2 Symmetry 1 11ba00
Configuration 3 Symmetry 1 11ab00
Configuration 4 Symmetry 1 1b1a00
Configuration 5 Symmetry 1 11b0a0
for triplet state in both cases i get the following configuration
Configuration 1 Symmetry 1 11aa00
Configuration 2 Symmetry 1 11a0a0
Configuration 3 Symmetry 1 1a1a00
Configuration 4 Symmetry 1 110aa0
as you can see SlaterDet option reverse ab to ba but not to aa
I want to get conical intersection or avoided crossing between
Configuration 1 Symmetry 1 111000 of singlet and
Configuration 1 Symmetry 1 11aa00 of triplet state
I sent this question to Gaussian team and their reply was not convincing to
me, I will put it here for your reference,
I think they just go around the problem to claim that there is no problem in
the manual
i think gaussian program can not do it
if i am wrong i will appreciate if you guide me
If i am write so what program can find this conical intersection for me
sorry for long email but i think it won't show my point if it is shorter
Dr. Ibrahim,
Thank you for giving us a chance to comment.
When you look at those configuration lists you are not actually
looking a lists of identical things. The singlet without Slater Determinant
is a list of configurations, fixed linear combinations of determinants
giving singlets. So there will be no triplet terms in this expansion
and the higher roots of the CASSCF equations will all be singlets as
well.
The second case lists determinants directly and generates singlets
and m(l)=0 triplets. So configurations 2 and 3 are a pair of determinants
which can contribute to both singlets and triplets with the sign difference
carried on the CI expansion coefficients, not on the determinants
directly.
The third case correspond to a ground state triplet, m(l)=+/-1
and no singlet contributions are possible. Again any excited states will
be triplets so this reference is not suitable for the crossing.
So the program can compute the crossing you desire by using a
singlet reference with SlaterDet included in the option list. You
should still solve for the first few roots to confirm that you have
the second root corresponding to the triplet you expected.E-mail to subscribers:
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Yavuz Dede
GÜ-Fen Fakültesi
Kimya Bölümü
L-128 06500 Ankara
Tel: 312-202-1386
Faks: 312-212-2279
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Yavuz Dede, Ph.D.
Theoretical/Computational Chemistry
Gazi University
Faculty of Science
Department of Chemistry
06500 Ankara TURKEY
http://w3.gazi.edu.tr/~dede/ydd.htm
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