Subject: Convergence problems in MNDO program

From: <[email-masked]>
Date: Tue, 13 Feb 1996 14:38:57 +0100

Dear netters,

I am using an old version of the MNDO program (QCPE No. 353) as a part of
another program (the so called DDRP) for determining reaction paths. The MNDO
program calculates the total energy values in various points of the potential
energy surface of the system investigated.
   Our main program is working without any problem, it is very stabil, but the
part - which is basically a truncated MNDO program - is very slow and often
doesn't converge at all.
   This version of MNDO contains an old iteration method of M. J. S. Dewar and
P. K. Weiner (Comput. Chem. 2,31,1978). Well, I determined to implement an
improved iteration algorithm developed especially for the MNDO program
(P. Badziag and F. Solms, Comput. Chem. 12,233,1988). This iteration algorithm
was very similar to that in the original program and I thought, it can be
built without any problem into the subroutine BORDER of the MNDO and other
parts of the program can remain unchanged. The algorithm of Badziag and Solms
was said to be superiour over other known methods (for example those
implemented into the program package AMPAC).
   Unfortunately the description of this algorithm was not enough to reproduce
this iteration method. I have tried to carry out this iteration scheme based on
the description with and without any change. The new version is working now
but my results are not very promising.
   It follows what I want to ask:

   1. Can somebody send me the improved subroutine BORDER - and perhaps also
      other parts of the program - which must be changed?

   2. Can you give me E-mail address of Badziag or Solms?

   3. Any other suggestion?

Thanks in advance any suggestion. If there is interest in this problem and I
receive any answer, I will write a summary.

                       Best regards    Dr. Gyula Domotor