From owner-chemistry@ccl.net Fri Apr 20 17:20:00 2012
From: "Nikita Matsunaga Nikita.Matsunaga-$-liu.edu"
To: CCL
Subject: CCL:G: Avoided crossing
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Date: Fri, 20 Apr 2012 15:16:25 +0000
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Sent to CCL by: Nikita Matsunaga [Nikita.Matsunaga()liu.edu]
You can calculate minimum energy crossing point between two states of different spins, such as singlet and triplet, in GAMESS. (In $CONTRL RUNTYP=MEX would do the trick.) The states of the same symmetry and spin can mix, and causes derivative coupling to be non-zero near or at either conical intersection or avoided crossing. There is no mixing between singlet and triplet states in the non-relativistic quantum chemistry, hence the two states have to cross. The states can mix when spin-orbit coupling is introduced.
Nikita
On Apr 20, 2012, at 8:47 AM, Abrash, Sam sabrash{}richmond.edu wrote:
>
> Sent to CCL by: "Abrash, Sam" [sabrash**richmond.edu]
> As far as I understand it, avoided crossings are always between states of the same symmetry, so there wouldn't be an avoided crossing between a singlet and a triplet state.
>
> Sam
>
> Samuel A. Abrash
> Department of Chemistry
> University of Richmond
> Richmond, VA 23173
> Phone: 804-289-8248
> Fax: 804-287-1897
> E-mail: sabrash|*|richmond.edu
> Web-page: http://www.richmond.edu/~sabrash
> "In 1893 Charles Hinton left Japan to become a mathematics instructor at Princeton University, where he invented a baseball-pitching machine that used gunpowder to propel the balls, like a cannon. After several accidents, the device was abandoned and Hinton lost his job ..." Terry Pratchett, Ian Steward and Jack Cohen, The Science of Diskworld III
>
> -----Original Message-----
>> From: owner-chemistry+sabrash==richmond.edu|*|ccl.net [mailto:owner-chemistry+sabrash==richmond.edu|*|ccl.net] On Behalf Of Walid M. I. Hassan walid_m76.:.yahoo.com
> Sent: Thursday, April 19, 2012 7:37 PM
> To: Abrash, Sam
> Subject: CCL:G: Avoided crossing
>
>
> 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.http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt>
>
仁城苔炳 松永
Nikita.Matsunaga]_[liu.edu