Subject: MOPAC2000 3D periodic file

From: <[email-masked]>
Date: Tue, 7 Aug 2001 09:47:58 +0000

Hi there,

am having a little trouble in getting MOPAC2000 to work with a 3D periodic model
and I was wondering if someone on this list had used MOPAC2000 for any system of
this sort and would be willing to send me an input file so that I can compare it
to what I have been using. The models I am trying to run are extended periodic
models of graphite. If anyone has an input file for a simple extended periodic
input file (no symmetry assumed) that works in MOPAC2000 then maybe I can guess
where I am going wrong! The systems I am trying to optimise are (pxqxr) models
reduced to a single unit cell with P1 symmetry (p,q,r are all integers).

I have tried using the MAKPOL facility with MOPAC2000 but it gives the same
input file for MOPAC2000 that I am already using, constructing such cells in
MOPAC2000 does not appear to be difficult at first sight for such models.

Incidentally the problem is that some of the atoms in the periodic model are
wandering a long way from their preferred positions and the structure is
buckling badly from the planar sheet of graphite atoms that we all are familiar
with. If there is any other theoretical reason why graphite should do this under
AM1 or PM3 semi-empirical then this would also be gratefully received.

Scott Owens

[email-masked]