Subject: Help: compare AM1, MM2 and ab initio. Help!!!

From: <[email-masked]>
Date: Thu, 18 Jan 1996 14:50:34 -0600 (CST)

Dear CCLer

I tried to get ground state geometries of EE, EZ, and ZZ   of 1,5-cylooctadiene from AM1
 under Dos version of MOPAC 7.0.  I want to compare them to the ab initio results of 
these geometries, but both results are quite different.  
   
       Relative energies from both calculation are

                   ZZ Geometry           |         |        EE geometry
-------------------------------------------------------------------
            twisted boat  half boat      chair   |    E,Z    |   Chair   twisted 
AM1         1.74        1.18         0.0                        25.72        23.16         

Ab initio   0.0          2.8          2.0             12.0        20.1     28.1

MM2          0.96         **          0.0                         35.52     28.24
 -------------------------------------------------------------------
     Ab initio calc from  Shimizu T., Iwata K. Kamigata N. and S. Ikata,  J. chem. 
                                     Research, 436-437 (1994)
     MM2 calc from PC Model 5.0 under the pentium PC.

I  am still working on these system.  If you have any comment about this, please
don't hesitate.  

Thanks in advance.

PS:  I would like to have  a manual of mopac 7.0 and some data and  any data of 
       cyclic system which is containing silicon atom on there  

             Daniel Jung
             Dept of Chemistry
             University of Houston