Collective Electronic Polarization Drives Charge Asymmetry at Oil-Water Interfaces
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arXiv
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| Format: | Preprint |
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2026
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| author | Amante, Gabriele Mrazikova, Klaudia Centi, Gabriele Roke, Sylvie Hassanali, Ali Cassone, Giuseppe |
| author_facet | Amante, Gabriele Mrazikova, Klaudia Centi, Gabriele Roke, Sylvie Hassanali, Ali Cassone, Giuseppe |
| contents | Why kinetically stable oil droplets in water spontaneously acquire a negative charge remains one of the most vigorously debated questions in interfacial science. Here, we combine neural-network based deep potential molecular dynamics with a data-driven and information theory approach to probe the real-space electron density at an extended decane-water interface. While decane-water clusters show nearly symmetric forward and backward charge transfer (CT) and thus negligible net CT, the extended interface displays a systematic electronic asymmetry, yielding a net CT from water to the hydrocarbon phase producing an average surface charge density of $\sim0.006~e^{-}\,\mathrm{nm}^{-2}$ on the oil phase. This imbalance is accompanied by much larger intra-phase self-polarization, particularly within the hydrocarbon phase, demonstrating that collective many-body polarization dominates the interfacial electronic response. Structural analysis reveals an asymmetry between forward C--H$\cdots$O and backward O--H$\cdots$C motifs, providing a microscopic origin for a net CT from one phase to the other. Curiously, both the water O--H and decane C--H covalent bonds incur subtle contractions which originate from a response to the charge-separation layers at the interface. These features are fully consistent with the weak improper hydrogen-bonds forming at the oil-water interface that results in blue-shifts of the C-H modes. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2603_24142 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Collective Electronic Polarization Drives Charge Asymmetry at Oil-Water Interfaces Amante, Gabriele Mrazikova, Klaudia Centi, Gabriele Roke, Sylvie Hassanali, Ali Cassone, Giuseppe Chemical Physics Soft Condensed Matter Computational Physics Why kinetically stable oil droplets in water spontaneously acquire a negative charge remains one of the most vigorously debated questions in interfacial science. Here, we combine neural-network based deep potential molecular dynamics with a data-driven and information theory approach to probe the real-space electron density at an extended decane-water interface. While decane-water clusters show nearly symmetric forward and backward charge transfer (CT) and thus negligible net CT, the extended interface displays a systematic electronic asymmetry, yielding a net CT from water to the hydrocarbon phase producing an average surface charge density of $\sim0.006~e^{-}\,\mathrm{nm}^{-2}$ on the oil phase. This imbalance is accompanied by much larger intra-phase self-polarization, particularly within the hydrocarbon phase, demonstrating that collective many-body polarization dominates the interfacial electronic response. Structural analysis reveals an asymmetry between forward C--H$\cdots$O and backward O--H$\cdots$C motifs, providing a microscopic origin for a net CT from one phase to the other. Curiously, both the water O--H and decane C--H covalent bonds incur subtle contractions which originate from a response to the charge-separation layers at the interface. These features are fully consistent with the weak improper hydrogen-bonds forming at the oil-water interface that results in blue-shifts of the C-H modes. |
| title | Collective Electronic Polarization Drives Charge Asymmetry at Oil-Water Interfaces |
| topic | Chemical Physics Soft Condensed Matter Computational Physics |
| url | https://arxiv.org/abs/2603.24142 |