New approach to molecular dynamics for a non-pairwise Hamiltonian

Abstract

In order to be able to simulate complex systems of non-pairwise additive interactions, a new computational approach, nth nearest neighbour network (n-NNN), has been proposed. In this new method, the continuous force acting on the central atom from its neighbours is a discretized multidimensional function based on the positions of the neighbours and stored in the computer memory. The memorized force is reused if an identical cluster neighbourhood is encountered once again. Here, the performance of the new method is evaluated for the 12–6 Lennard-Jones fluid and found to give reasonably accurate values for the thermodynamic properties. The algorithm is just as fast with many-body forces, as it is with pairwise additivity. The efficiency of the algorithm is demonstrated by applying it to MD simulations that explicitly incorporate three-body forces, and then comparing the computer time with the same simulation performed with conventional MD methods. The new n-NNN approach, although fast and accurate, is dependent on large amounts of computer memory. Suggestions are made to further improve the method.