LARGE TIMESTEPS IN MOLECULAR DYNAMICS SIMULATIONS

Both equilibrium and nonequilibrium molecular dynamics simulations are carried out for two state points of the Lennard-Jones fluid, using leapfrog algorithms. In the equilibrium simulations we obtain internal energies, pressures, radial distribution functions and velocity autocorrelation functions. In the nonequilibrium simulations we obtain the relevant transport coefficients; additionally, the radial distribution function and velocity autocorrelation function in a shearing fluid are computed. It is found that, provided the accuracy of the particle trajectories is fully utilised in calculating their velocities, much larger timesteps than are customary can be used without significant drift in the results. We are thus able to take full advantage of the well known stability of the leapfrog algorithm and also of the even greater stability of its modifications for isokinetic simulations.