c CCLRC
Section 5.1
(b) r
vdw
- the user-specified cutoff for the van der Waals potentials set by rvdw. If not
specified its value defaults to r
cut
.
13. Constraint algorithms in DL POLY 3 , SHAKE/RATTLE (see Section
ation precision of 10
-8
and limit of iteration cycles of 250. Users may experience that during
optimisation of a new built system containing constraints simulation may fail prematurely
since a constraint algorithm failed to converge. In such cases directives mxshak (to increase)
and shake (to decrease) may be used to decrease the strain in the system and stablise the
simulation numerics until equilibration is achieved.
14. DL POLY 3 's DD strategy assumes that the global density of a system does not vary much
during a simulation, which is not the case in extremely non-equilibrium simulations or some
specific systems. A way to tackle such circumstances and avoid simulations crash is to use
the densvar f option. In the set bounds subroutine DL POLY 3 makes assumptions at
the beginning of the simulation and corrects the lengths of link-cell (mxlist) and domain
(mxatms) lists arrays when the option is activated with f > 0. Greater values of f will
correspond to allocation bigger global arrays and larger memory consumption by DL POLY 3
during the simulation. Note that this option may demand more memory than available on
the computer architecture. In such cases DL POLY 3 will terminate with an array allocation
failure message.
15. As a default, DL POLY 3 does not store statistical data during the equilibration period. If
the directive collect is used, equilibration data will be incorporated into the overall statistics.
Users are advised to study the example CONTROL files appearing in the data sub-directory to see
how different files are constructed.
5.1.2
The CONFIG File
The CONFIG file contains the dimensions of the unit cell, the key for periodic boundary condi-
tions and the atomic labels, coordinates, velocities and forces. This file is read by the subroutine
read config. (It is also read by the subroutine scan config in the set bounds routine.) The
first few records of a typical CONFIG file are shown below:
IceI structure 6x6x6 unit cells with proton disorder
2
3
26.988000000000000
0.000000000000000
0.000000000000000
-13.494000000000000 23.372293600000000
0.000000000000000
0.000000000000000
0.000000000000000
44.028000000000000
OW
1
-2.505228382
-1.484234330
-7.274585343
0.5446573999
-1.872177437
-0.7702718106
3515.939287
13070.74357
4432.030587
HW
2
-1.622622646
-1.972916834
-7.340573742
1.507099154
-1.577400769
4.328786484
7455.527553
-4806.880540
-1255.814536
HW
3
-3.258494716
-2.125627191
-7.491549620
2.413871957
-4.336956694
2.951142896
83