Approved for Public Release Long-range Lattice-Gas Algorithm

Presented is a novel algorithmic method for simulating complex fluids, for instance multiphase single component fluids and molecular systems. The algorithm falls under a class of single-instruction multiple-data com-putation known as lattice-gases, and therefore inherits exact computabil-ity on a discrete spacetime lattice. Our contribution is the use of nonlocal interactions that allow us to model a richer set of physical dynamics, such as crystallization processes, yet to do so in a way that remains locally computed. A simple computational scheme is employed that allows all the dynamics to be computed in parallel with two additional bits of local site data, for outgoing and incoming messengers, regardless of the number of long-range neighbors. The computational scheme is an ecient decom-position of a lattice-gas with many neighbors. It is conceptually similar to the idea of virtual intermediate particle momentum exchanges that is well known in particle physics. All 2-body interactions along a particular direction dene a spatial partition that is updated in parallel. Random permutation through the partitions is sucient to recover the necessary isotropy as long as enough momentum exchange directions are used. The algorithm is implemented on the CAM-8 prototype. i Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information