Hi Adam,
Thanks for your reply.
In normal geometry optimisations, 180 degree angles are quite nicely
handled by present version of ADF. In this case, restarting an IRC run
causes the problem which gives these errors at very first step.
Otherwise an initial IRC run proceeds smoothly until I restart it at
certain point. Similarly problem never occured during linear transit
runs or their restarts.
May be "atoms" keyblock should also be refreshed at the restart.

Masroor

On Tue, Sep 27, 2005 at 02:28:11PM +0100, Adam Sykes wrote:
> Hi Masroor,
>
> I am not certain for ADF, but, I think when using Z-matrices, programs do
> not like changes in bond angle of more than 180 degrees. I think this can
> be avoided by inclusion of Dummy Atoms to split the angle up before
> minimisation.
>
> I'm sure someone else could provide you with a more ADF specific answer.
>
> Adam Sykes
> The University of Liverpool
>
>
> -----Original Message-----
> From: owner-adf-list_at_scmserver.chem.vu.nl
> [mailto:owner-adf-list_at_scmserver.chem.vu.nl] On Behalf Of Masroor Ahmad
> Sent: 27 September 2005 13:46
> To: adf-list_at_scm.com
> Subject: ADF-LIST: Z-matrix error in IRC restarts
>
> Hi list,
> I am having problem while restarting IRC runs. At every restart error
> occurs during geometry step with following messages:-
>
> ADF EXIT called
> pp info: terminating timer Geop.geostpi
> Serious error in determine_zmat_displace adjusting bond angle
>
> and also:-
>
> <Sep25-2005> <13:08:33> >>>> ENGRAD
> <Sep25-2005> <13:09:10> WARNING: dihedral jumps 180 degrees
> <Sep25-2005> <13:09:10> ... check your bond angles
> <Sep25-2005> <13:09:10> WARNING: dihedral jumps 180 degrees
> <Sep25-2005> <13:09:10> ... check your bond angles
> <Sep25-2005> <13:09:10> WARNING: dihedral jumps 180 degrees
> <Sep25-2005> <13:09:10> ... check your bond angles
> <Sep25-2005> <13:09:10> E-test: old,new= 0.00000, -4.50020 hartree
> <Sep25-2005> <13:09:10> max gradient: 0.15368484 au/angstrom,radian
> <Sep25-2005> <13:09:10> max bond step: 1.10897534 angstrom
> <Sep25-2005> <13:09:10> max angular step:103.08254259 degree
> <Sep25-2005> <13:09:10> WARNING: Bond angle appears to have passed through
> 0 or 180 degrees during geometry optimization. This should be avoided by
> introducin
> <Sep25-2005> <13:09:10> Serious error in determine_zmat_displace adjusting
> bond angle
> <Sep25-2005> <13:09:10> WARNING: not all scratch files were closed
> <Sep25-2005> <13:09:10> END
> --
>
> Your's truly
> Masroor Bangesh
>
> -------------------------------------------------|
> Institute für Anorganische und Analytische Chemie|
> Friedrich-Schiller Universität Jena |
> Carl-Zeiss Promenade 10 |
> D-07743 Jena (Germany) |
> -------------------------------------------------
> PLEASE NOTE NEW TELEPHONE NO:-
> -------------------------------------------------|
> Tel: +49(0)3641-948135 |
> -------------------------------------------------|
>
> P.S:- I used same "atoms" keyblock in restart run, corresponding to
> initial geometry of T.S.
>

-- 
Your's truly
Masroor Bangesh
-------------------------------------------------|
Institute für Anorganische und Analytische Chemie|
Friedrich-Schiller Universität Jena              |
Carl-Zeiss Promenade 10                          |
D-07743 Jena (Germany)                           |
-------------------------------------------------
PLEASE NOTE NEW TELEPHONE NO:-
-------------------------------------------------|
Tel: +49(0)3641-948135                           |
-------------------------------------------------|