CCL: DLPOLY error mesage



 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