Appendix A
DL POLY 3 Periodic Boundary
Conditions
Introduction
DL POLY 3 is designed to accommodate a number of different periodic boundary conditions, which
are defined by the shape and size of the simulation cell. Briefly, these are as follows (which also
indicates the IMCON flag defining the simulation cell type in the CONFIG file - see
1. None e.g. isolated polymer in space (imcon = 0)
2. Cubic periodic boundaries
(imcon = 1)
3. Orthorhombic periodic boundaries
(imcon = 2)
4. Parallelepiped periodic boundaries
(imcon = 3)
5. Slab (X,Y periodic; Z non-periodic) (imcon = 6)
We shall now look at each of these in more detail. Note that in all cases the cell vectors and the
positions of the atoms in the cell are to be specified in Angstroms (°
A).
No periodic boundary (imcon = 0)
Simulations requiring no periodic boundaries are best suited to in vacuuo simulations, such as
the conformational study of an isolated polymer molecule. This boundary condition is not recom-
mended for studies in a solvent, since evaporation is likely to be a problem.
Note this boundary condition have to be used with caution. DL POLY 3 is not naturally suited to
carry out efficient calculations on systems with great fluctuation of the local density in space, as is
the case for clusters in vacuum. The parallelisation and domain decomposition is therefore limited
to eight domains (maximum of two in each direction in space).
This boundary condition should not used with the SPME Ewald summation method.
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