*From*: "Mr Mi Yang" <agri_chemist%yahoo.com>*Subject*: CCL:G: Opt with Full point group Symmetry in G09*Date*: Wed, 28 Mar 2012 02:18:44 -0400

Sent to CCL by: "Mr Mi Yang" [agri_chemist\a/yahoo.com] First of all thanks for replies of Jimenez Vazquez, Cory Pye and others. Actually, I have used Z-matrix made by molden and it works perfect to maintain symmetry in G09 only for small molecules like benzene. But for a Fulleren like molecule to build Z-matrix manually is almost impossible. Is there any software which can help to build Z-matrix for 3 dimensional fulleren like big molecule by using some dummy atoms so that it can maintain symmetry in G09 opt...? I observed below mentioned problem in most of molecules with DnD or DnH symmetries where G09 try to maintain largest Abelian group instead of full point group. I have not included any diffused function in basis set but will check a bigger set without diffused function. regards, Mr.MiYang > "Hugo Alejandro Jimenez Vazquez hjimenez],[woodward.encb.ipn.mx" wrote: > > Sent to CCL by: Hugo Alejandro Jimenez Vazquez [hjimenez,+,woodward.encb.ipn.mx] > > Although MiYang does not mention it, I would guess that he is using > diffuse functions in the basis set employed in his (her?) calculations. > I am also trying to do calculations on fullerenes, and I have found that > the inclusion of diffuse functions breaks the symmetry of the wavefunction > with respect to the symmetry of the molecule under analysis. Gaussian says > that "the density has only Abelian symmetry" and in an optimization the > point group of the molecule changes to that of the density with the > corresponding increase in computational cost. I have not found a way to > solve this problem other than getting rid of the diffuse functions from > the basis set, although I am still looking. I asked for advise from > Gaussian, but they could not help me. The problem is not particular to > Gaussian 09; previous versions of Gaussian also exhibit the same behavior. > > Another solution would be to use a larger basis set withouth the use of > diffuse functions. I have not tried Cory's suggestion though, but I > believe that the outcome would be the same. > > Regards, > > > -- > --- > Hugo A. Jimenez Vazquez > hjimenez###woodward.encb.ipn.mx > Departamento de Quimica Organica > ENCB-IPN > Mexico > > > > On Tue, 27 Mar 2012, Cory Pye cpye : ap.smu.ca wrote: > > > > > Sent to CCL by: Cory Pye [cpye|,|ap.smu.ca] > > Hello Mi, > > > > I recommend the use of opt=z-matrix and a very carefully constructed z-matrix. > > > > -Cory Pye > > > > On Sun, 25 Mar 2012, Mi Yang agri_chemist%x%yahoo.com wrote: > > > > > > > > Sent to CCL by: "Mi Yang" [agri_chemist++yahoo.com] > > > Dear CCL Colleagues, > > > I am desperately trying to optimized a C 40 fulleren molecules with D5d symmetry. But after my > > > several calculations with different coordinates it reduces the symmetry C2H in final geometry. I > > > checked CCL archives and used some helpful keywords like symm=loose and iop(2/17=xx), > > > iop(2/18=xx) upto 1 etc. > > > > > > Do Gaussian has ability to optimized only some systems in their Largest Abelian subgroup instead of > > > full point group...? > > > In my comparison of systems same point group is necessary so how can I optimized the above Fulleren > > > 40 (D5d) system in G09...? > > > Any comment or recommendation will be highly appreciating..... > > > > > > MiYang> > > > > > > > ************* ! Dr. Cory C. Pye > > ***************** ! Associate Professor > > *** ** ** ** ! Theoretical and Computational Chemistry > > ** * **** ! Department of Chemistry, Saint Mary's University > > ** * * ! 923 Robie Street, Halifax, NS B3H 3C3 > > ** * * ! cpye]^[crux.stmarys.ca http://apwww.stmarys.ca/~cpye > > *** * * ** ! Ph: (902)-420-5654 FAX:(902)-496-8104 > > ***************** ! > > ************* ! Les Hartree-Focks (Apologies to Montreal Canadien Fans) > > > >