Interplay of ion availability and mobility in the loss of cation selectivity for CaCl\textsubscript{2} in negatively charged nanopores: molecular dynamics using scaled-charge models
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| Format: | Preprint |
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2026
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| _version_ | 1866917441674674176 |
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| author | Shabbir, Salman Boda, Dezső Ható, Zoltán |
| author_facet | Shabbir, Salman Boda, Dezső Ható, Zoltán |
| contents | Ion transport through charged nanopores is commonly interpreted in terms of electrical double layer structure, leading to the expectation of cation-selective conduction in negatively charged pores. This picture can break down for multivalent electrolytes, where strong ion-urface correlations and charge inversion modify transport behavior. Here, we study NaCl and CaCl$_2$ conduction through negatively charged silica nanopores using atomistic molecular dynamics simulations with scaled-charge ion models. By separating concentration and velocity contributions to the radial particle current density, we connect static adsorption to dynamic perm-selectivity. While NaCl exhibits conventional cation selectivity, CaCl$_2$ shows nearly bulk-like or even anion-favored transport due to Ca$^{2+}$ immobilization near the surface and dominant Cl$^-$ conduction in the pore interior following charge inversion. Although this qualitative mechanism is robust, its detailed manifestation depends sensitively on the balance of ion-surface and ion-water interactions encoded in the force field. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_10600 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Interplay of ion availability and mobility in the loss of cation selectivity for CaCl\textsubscript{2} in negatively charged nanopores: molecular dynamics using scaled-charge models Shabbir, Salman Boda, Dezső Ható, Zoltán Statistical Mechanics Ion transport through charged nanopores is commonly interpreted in terms of electrical double layer structure, leading to the expectation of cation-selective conduction in negatively charged pores. This picture can break down for multivalent electrolytes, where strong ion-urface correlations and charge inversion modify transport behavior. Here, we study NaCl and CaCl$_2$ conduction through negatively charged silica nanopores using atomistic molecular dynamics simulations with scaled-charge ion models. By separating concentration and velocity contributions to the radial particle current density, we connect static adsorption to dynamic perm-selectivity. While NaCl exhibits conventional cation selectivity, CaCl$_2$ shows nearly bulk-like or even anion-favored transport due to Ca$^{2+}$ immobilization near the surface and dominant Cl$^-$ conduction in the pore interior following charge inversion. Although this qualitative mechanism is robust, its detailed manifestation depends sensitively on the balance of ion-surface and ion-water interactions encoded in the force field. |
| title | Interplay of ion availability and mobility in the loss of cation selectivity for CaCl\textsubscript{2} in negatively charged nanopores: molecular dynamics using scaled-charge models |
| topic | Statistical Mechanics |
| url | https://arxiv.org/abs/2602.10600 |