A simple time coarse graining method for molecular dynamics simulations of liquids

Abstract: Considering molecular dynamic simulations as a stochastic method, we investigate the possibility of time coarse graining the simulations. Similarly to Boltzmann inversion method in spatial coarse graining, which begins with a free energy called potential of mean force, we test the effect of a generalized potential of mean force that uses the distinct part of the Van Hove correlation function with a characteristic time different from zero. We show that the method is approximately equivalent to replace the hard core of the original potential by a smooth harmonic function. We then compare the results of simulations using the modified potential and the original one. Results show that this simple modification of the potential, namely replacing the short range wall with a smooth quadratic law, leads to a shift in the time step resulting in the same dynamics than the original potential function but with a much larger time step.