Error in the Debye–Hückel approximation for dilute primitive model electrolytes with Bjerrum parameters of 2 and ca. 6.8 investigated by Monte Carlo methods. Excess energy, Helmholtz free energy, heat capacity and Widom activity coefficients corrected for neutralising background

摘要: Monte Carlo (MC) simulations have been performed for primitive model electrolytes with a Bjerrum parameter B= 2 five values of κa in the region ca. 0.022–0.11. Also, an extremely dilute : electrolyte (B= 6.8116 and 0.0276) has investigated. Between eight million configurations used each simulation, number ions simulation (N) was varied between 32 1728. The universal scaling results using ratio Debye length to half period periodic boundary conditions (minimum image cut-off distance), which found systems 1, 1.546 1.681 earlier paper, is hold also present simulations. In this way, precise extrapolations excess energies (Eex/NkT), electrostatic Helmholtz free heat capacities can be found.By means analytic correction Widom test particle method activity coefficients most variation, (N), chemical potentials may removed. trick introduce homogeneous neutralising background. N-dependence left scales exactly like Eex/NkT, so that extrapolated found.The deviations from Debye–Huckel increase increasing B(at fixed κa). With 2, all thermodynamic quantities except capacity are situated law limiting law. κa≈ 0.0276, however, on ‘wrong’ side law, very large, e.g. 40% Eex/NkT 400–500% capacity. These well accounted by DHX theory, electric potential around central ion as mean force.