From chemistry-request ^at^ ccl.net Thu Jun 18 14:03:23 1992
Date: Thu, 18 Jun 92 11:02:13 CDT
From: george -8 at 8- archimedes.cray.COM (George Fitzgerald)
Subject: MOPAC 6 bug
To: chemistry:~at~:ccl.net
Status: R

Manish Sud writes:
> Using keyword ESP in conjunction with MULLIK in MOPAC 6.0 generates 
> excessively large values for the charges - scaled and unscaled - for 
> any molecular system.

I have traced this to the use of the array C in COMMON/VECTOR/.
In routine MULLIK, C is used as scratch, so the eigenvectors are
destroyed.  Unfortunately, the esp routines expect to find the eigenvectors
in that array.  I solved this problem in my own version by creating a scratch
array of size MORB2 in routine WRITMO (which calls MULLIK).  I saved a copy 
of C at the start of WRITMO, and copy it back into C at the end of WRITMO.
I realize that there are more elegant solutions, but this was the quickest one
I could code up.

Does anybody know of a formal way to submit this fix to QCPE?

George Fitzgerald
Cray Research, Inc.
george- at -gravity.cray.com