Thermostat choice significantly influences water flow rates in molecular dynamics studies of carbon nanotubes

Extremely rapid water flow through carbon nanotubes has been observed in both experiment and simulation which has led to the suggestion that this material be used in a number of filtration applications. However, there is significant disparity in the magnitude of water permeability and the degree of flow enhancement compared with conventional porous materials in the literature. Here, we show that one of the causes of the disparity in simulation data is the variety of methods used to control temperature in molecular simulations. Not only can the choice of thermostat alter the flow rate and permeability by as much as five times, but it can determine whether the transport is observed to be frictionless or not. In addition to helping explain the disparate simulation results on transport in nanomaterials, this work provides some guidelines to help designing and interpreting molecular simulations of mass transport.