A minimal model of ionic aggregation in concentrated ZnCl2 is developed, guided by molecular dynamics simulations with a machine-learned potential. It explicitly incorporates solvent-site depletion, correlated chloride binding, and allows for loops within Zn-Cl clusters. Dehydration is shown to drive ion binding through two sharp transitions set by the Zn coordination number Z: a crossover at Z=2 from isolated ions to Cl-bridged clusters, and gelation near Z≈3. The model agrees quantitatively with MD results, and the critical exponent of the cluster-size distribution matches percolation theory.
@article{arxiv.2512.18167,
title = {Dehydration-Driven Ion Aggregation and the Onset of Gelation in ZnCl$_2$ Solution},
author = {Alexei V. Tkachenko and Chuntian Cao and Amy C. Marschilok and Deyu Lu},
journal= {arXiv preprint arXiv:2512.18167},
year = {2025}
}