From owner-chemistry@ccl.net Thu Aug 7 14:49:02 2008 From: "Hemant Srivastava hemantkrsri%gmail.com" To: CCL Subject: CCL:G: Crysallographic structure Vs optimized Message-Id: <-37508-080807113018-30662-VnuubneqKp0u71cLiWQJbA^server.ccl.net> X-Original-From: "Hemant Srivastava" Content-Disposition: inline Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Date: Thu, 7 Aug 2008 18:30:02 +0300 MIME-Version: 1.0 Sent to CCL by: "Hemant Srivastava" [hemantkrsri+*+gmail.com] Dear Shabbir, For fixing diahedral angle you can write following in input file al last. D 1 2 3 4 F where 1 2 3 4 are atom numbers. For the other problem you have I think you should try different method/basis or solvent calculation. Hope it will help. Hemant Kumar Srivastava, The Hebrew University of Jerusalem =================================== On 8/6/08, Mr shabbir shabbir*_*nenu.edu.cn wrote: > > Sent to CCL by: "Mr shabbir" [shabbir__nenu.edu.cn] > Hello CCL users! > I am a in some confusion want to explain it. Please If some one have an idea let me know also. > I have taken a crystallographic structure and optimized it using Gaussian03 with C2 symmetry and b3lyp/6-31G* method. After optimization it gave me a round about planer structure. After this I have calculated its UV and IR spectra that is in good agreement with experimental values but the crystallographic structure has a dihedral angle 40 degree with side pyrrol rings which is not in my optimized structure. So can I say that my Gassphase optimized structure is reliable on the basis of calculated experimental values and start my futher calculations? Secondly I tried to freeze that dihedral angle using guessview but it could not freeze during optimization. How to freeze dihedral angle during optimization so that it will not change during calculations? > Mr.Shabbir > Northeast normal university Changchun > P.R.China > shabbir++nenu.edu.cn> > >