The chemical-potential in atomically inhomogeneous fluids in external force fields by computer-simulation

The accuracy and practicality of the Widom fictitious-particle insertion method for determining the chemical potential is tested for very inhomogeneous fluids in strong external potentials by a series of molecular dynamics computer simulations. The chemical potential determined in this way is found, as predicted, on an atomic scale to be independent of position in the fluid to a few percent even when the density varies by up to a factor 80. This severe test means that this method of determining chemical potential is established as reliable and accurate in any well-found computer simulation even when the system is very inhomogeneous.