CCL: DLPOLY error mesage
- From: "Ozgur Yazaydin" <yazaydin*WPI.EDU>
- Subject: CCL: DLPOLY error mesage
- Date: Wed, 27 Sep 2006 04:25:59 -0400 (EDT)
Sent to CCL by: "Ozgur Yazaydin" [yazaydin::WPI.EDU]
On Tue, September 26, 2006 4:48 pm, sabri alkis alkis . ufl.edu wrote:
> Sent to CCL by: "sabri alkis" [alkis*o*ufl.edu]
> Dear all,
>
> I have 6329 atoms(alkanthiol monolayer on gold surface and a silver
> cluster on top of these molecules) I used UFF(universal force field)
> parameters to calculate the vdw parameters between the atoms. When I run
> the simulation, I keep getting this error message "1-4 separation
exceeds
> cutoff range". I tried different cutoff values but I got the same
error
> message again.. I looked at the source code but I do not know why I got
> this message. What do u guys think the problem is? Is it wrong vdw
> parameters? What could I try?
Sabri,
This error message means that 1st and 4th atoms sharing the same dihedral
structure are far away from each other that it is not normal. At the end
of DL_POLY manual there is a section where the meaning of each error is
explained. You can't overcome this error by changing the cutoff distance.
Based on my experience, most of the time this error indicates that there
is something wrong with your force field parameters..
so make sure your parameters and energy units in the FIELD file are
correct. dl_poly handles the 1-4 interactions in the dihedral angle term.
In the FIELD file where you specify the dihedral angle, the last two terms
in each line are reserved for 1,4-vdw scaling and 1,4 coulombic scaling.
As far as I know in UFF force field 1-4 interactions are computed without
any scaling so make sure that those two parameters are set to 1.0.
I also reccommend you to post questions regarding DL_POLY to the DL_POLY
discussion forum which can be reached at
http://www.cse.clrc.ac.uk/disco/forums/postlist.php?Cat=0&Board=dlpoly
you can post your FIELD file and folks over there are very helpful to
examine your input files...
hope this helps
--
Ozgur YAZAYDIN
http://www.wpi.edu/~yazaydin
Department of Chemical Engineering
Worcester Polytechnic Institute
100 Institute Rd.
Worcester, MA 01609-2280 USA