DL_POLY version 4: a major shift in length- and time-scale limitations in Molecular Dynamics simulations of heterogeneous phenomena

DL_POLY is a computer program for parallel computers that is used by scientists to model atomic systems. It uses the method known as `molecular dynamics' to describe how atoms in a bulk material move in relation to each other and from this it is possible to obtain valuable information on the structure and properties of the bulk system as well as detailed insight into how the atoms behave individually. DL_POLY has been used for many years on some of the most powerful supercomputers available, but now an upgrade is needed to run the program successfully on the next generation of machines. The principal modifications required will help the program (i) to efficiently handle systems which either possess, or evolve into, highly nonuniform structures; (ii) handle systems which evolve very slowly in real time, through a series of very fast but very infrequent atomic `jumps' , which includes most solid state systems; and (ii) exploit the architecture of new supercomputers to gain maximum performance. These modifications will allow users of DL_POLY to study catalysis, biological systems, radiation damage and a host of other applications.