Background

The standard thermodynamic treatment of the chemical potential is reviewed. First, the [chemical potential of an ideal gas](chemical potential of an ideal gas) is introduced, as it presents a framework for treating real (non-ideal) systems. The [chemical potential of a real system](chemical potential of a real system) is then considered as a perturbation of the ideal gas result, where the fugacity coefficient describes the magnitude of the perturbation. The concept of the [ideal solution](ideal solution) is discussed, and the chemical potential is expressed as a perturbation of the ideal solution result, with the activity coefficient describing the magnitude of this perturbation.

The [relationship of chemical potential to diffusion and phase equilibrium](relationship of chemical potential to diffusion and phase equilibrium) is examined. This section shows why, under special conditions, concentration acts as the driving force for diffusion. [The fugacity](The fugacity) of a species in a fluid, which the partial pressure of the species in an ideal-gas phase in equilibrium with the fluid, is related to the chemical potential and is often more convenient to use for addressing diffusion and phase equilibrium.

Next it is shown [how the chemical potential depends on molecular interactions](how the chemical potential depends on molecular interactions). From this dependence, the [variation of chemical potential with pressure and composition](variation of chemical potential with pressure and composition) can be understood.

Finally, the [simulation model and methods](simulation model and methods) are presented.

Next: [chemical potential of an ideal gas](chemical potential of an ideal gas)