Boltzmann ion densities in a symmetric electrolyte (source code)

= Boltzmann ion densities in a symmetric electrolyte
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For point <ions> of charge $\pm e$ in potential $\psi$, equilibrium electrochemical potentials give $n_\pm=n_0\exp[\mp e\psi/(k_BT)]$, with $n_0$ the reservoir <density> of each species. The charge <density> is $-2en_0\sinh[e\psi/(k_BT)]$. A negative wall enriches positive <counterions> and depletes negative <co-ions>.