*From*: Nikita Matsunaga <Nikita.Matsunaga(~)liu.edu>*Subject*: CCL:G: Avoided crossing*Date*: Fri, 20 Apr 2012 15:16:25 +0000

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