A simple test for evaluating the truncation effects in simulations of systems involving charged groups

We report the results from a molecular dynamics (MD) simulation on a 1.0 M aqueous NaCl solution using the classical SPC water model and a treatment of long-range electrostatic forces involving a 9–16 Å twin-range cut-off. This study was undertaken to explore the importance of truncation effects in simulations involving charged species which employ cut-offs at longer range than typically used in MD. Artefacts were discerned in the ion-ion radial distribution functions at ≈ 16 Å, indicating that increasing the length scale of the truncation scheme does not necessarily lead to reliable trajectories. Our results indicate that ‘charge group-charge group’ radial distribution functions are a sensitive test for the detection of artefacts due to truncation and it is suggested that they should be used as a routine screening device in the analysis of MD systems involving charged groups.