Subject: MOPAC C.I.

From: [email-masked] (Jason Lye)
Date: Wed, 14 Feb 96 09:35:21 -0500

Dear netters,

I am in the process of investigating the excited states of aromatic (dye) 
molecules and I am using MOPAC for these studies.  As there are many low-lying 
excited electronic configurations, I use the C.I.= keyword, and the appropriate
ROOT= value, as well as specifing the mulitplicity.

Quite often, MOPAC will exit with the error message, "Degenerate Energy levels
detected in MECI...  MOPAC quits."
 
I have summarised responses which give explainations for this problem in the 
past.  Basically, if there are degenerate configurations for an excited system,
then either all or none of these must be included in the C.I. calculation.  
This can be achieved by using a higher or lower C.I. value to include or 
exclude all of the set of degenerate configurations.

There is a more sensitive approach, which involves the use of the keyword OPEN

My question is simply How do I use this keyword.  Could somebody please give
an example of how I could use this keyword to exclude or include all of the
degerate configurations in a C.I. calculation (eg C.I.=5)

As always, I will summarize.

Jason 

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Jason Lye,                       |    
Dye Synthesis Research Group,    |    
College Of Textiles,  Box 8301,  |     "If we did'nt have any bones, 
North Carolina State University, |      we would have to live in a bucket."
Raleigh, N.C. 27695 - 8301       |     
                                 |      
      Ph:   (919) 515-6615       |                     
      [email-masked]           |         
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