Neighbor lists a time-saving trick

In the inner loops of both Monte Carlo and molecular dynamics algorithms we consider particle i and loop over all other particles j to calculate the distance and the minimum image separations. If the distance is less than the potential cutoff distance, the interaction potential and the forces are computed. In this manner, all pairs of particles are examined 

List radius Update interval CPU time(s) N = 256 CPU tkne(s) N =512 

For Lennard-Jones fluids. Table 14.4 gives indicative values for list sizes and update frequencies for systems of two different sizes, with N = 256 and Af = 512 particles. The CPU time is shown that is required for calculation of the total potential energy for the different cases. As observed, there is an optimum list radius and update frequency. Notably, the optimum depends on the size of the system. 

AUen and D. J. Tildesley, Computer Simulation of Liquids, (New York Oxford University Press, 1989). 

Frenkel and B. Smit, Understanding Molecular Simulation, 2nd ed., (San Diego Academic, 2002). 

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