Molecular dynamics simulation of ions in charged capillaries

Electroneutrality and chemical potential balance in conventional models for ions in charged capillaries are discussed. The Poisson-Boltzmann (PB) equation and molecular dynamics (MD) simulation of ions inside an infinitely long charged pore show that inconsistencies exist. The PB solution shows that chemical potentials of individual ions are the same and electroneutrality is obeyed provided that the correct boundary condition is used at the wall. The MD simulations show that for a neutral system, the chemical potentials of the ions are different and hence they cannot be in equilibrium with a bulk solution. Modifications of existing models and set-ups of simulations are necessary to model the behaviour of ions in capillaries in equilibrium with a bulk solution.