Subject: Re: CCL:MOPAC Error Message.

From: </G=Matthew/S=Harbowy/OU=LIPTONUS-EC02/O=TMUS.TJL/@LANGATE.gb.sprint.com>
Date: Mon, 30 Oct 1995 11:30:00 -0500

The error meassage occurs because you have chosen seven orbitals for a c.i. 
calculation, and one of the two on the extrema of this selection is 
near-degenerate with one not selected. You either need to tell MOPAC how many 
filled orbitals you want (c.i.=7,n) where n is the number of filled orbitals, so
that you select ones that are non-near-degenrate, or need to expand or reduce 
your c.i. Convergence isn't going to help you fix the error message: the problem
may float in and out because the orbitals will move slightly with optimization.

matt

______________________________ Reply Separator _________________________________
Subject: CCL:MOPAC Error Message.
Author:  [email-masked] at INTERNET
Date:    10/29/95 2:10 AM

Dear Net-surfers,
     
I am attempting to use MOPAC 6.0 to construct Jablonski diagrams for several 
dyes, and for now I am interested in the singlet excited state energies.  I am 
using the PM3 optimised structure (gradient approx.=1) as my input for several 
SCF energy calculations, to obtain excited state energies in which I used the 
following keywords (PM3):
     
SINGLET C.I.=7 ROOT={n+1}               Where n=1,2,3,4,5,6
                                        For S1, S2, S3, respectively.
     
Unfortunatly, in the case of several structures, MOPAC stopped and returned an 
error message, viz:
     
`Degenerate energy levels detected in the MECI.  Some of these levels would be 
treated by MECI, while others would not.  This would lead to non-reproducable 
electronic energies.
Job stopped;  to continue specify GEO-OK."
     
I added the keyword PRECISE to try and tighten the SCF convergence criteria, 
however, this seemed to have no effect.
     
Reluctantly, I added the keyword GEO-OK and the energy levels were returned as 
expected, but.......
     
*  Could someone please tell me:
     
a)      What does the abovementioned error message really mean?  Does it refer
        to M.O.s or states or something else in the C.I. calculation?
b)      How can I avoid generation of the message?
c)      What are the consequences of specifying GEO-OK?
     
I have also come across the same scenario when dealing with excited state 
geometry optimizations in the past, and once again, the only way around them 
seemed to be to use GEO-OK.  I am concerned that by using this keyword, I am 
forcing the calculation to continue to completion when something is inherently 
problematic in my structure.
     
I intend to summarise my responses to this question and post it to the list, as 
I did before.
     
Thank you,
Jason.

_______________________________________________________________________________
     
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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