From owner-chemistry@ccl.net Thu Aug 7 10:44:00 2008 From: "Mr shabbir shabbir*_*nenu.edu.cn" To: CCL Subject: CCL:G: Crysallographic structure Vs optimized Message-Id: <-37501-080806075208-8167-sKFt/Hgs6iQYNm6ZnvScbw-#-server.ccl.net> X-Original-From: "Mr shabbir" Date: Wed, 6 Aug 2008 07:52:02 -0400 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