I thought a container wall is impenetrable due to Coulomb repulsions, but I realized that an idealized positively charged cylindrical container is not able to contain positive charges at all. So what else is the interaction at the container walls that prohibits particles to espace? Is it some effect of both polarities of the charges? Or a dynamical dipole effect? Or even quantum mechanical exchange repulsion? Which potential should I take to model the rebounce of neutral or charged particles at boundary walls?