Grain boundary melting in ice

TL;DR

This study investigates the factors influencing grain boundary melting in ice, demonstrating how electrostatic and colligative effects, modulated by dopants, affect premelted film thickness.

Contribution

It provides experimental insights into how electrolyte concentration and surface charge influence grain boundary premelting in ice, considering two theoretical limits.

Findings

Premelted film thickness increases with electrolyte concentration.

Electrostatic and colligative effects are key in grain boundary melting.

Dopant ions can manipulate premelting behavior.

Abstract

We describe an optical scattering study of grain boundary premelting in water ice. Ubiquitous long ranged attractive polarization forces act to suppress grain boundary melting whereas repulsive forces originating in screened Coulomb interactions and classical colligative effects enhance it. The liquid enhancing effects can be manipulated by adding dopant ions to the system. For all measured grain boundaries this leads to increasing premelted film thickness with increasing electrolyte concentration. Although we understand that the interfacial surface charge densities $q_s$ and solute concentrations can potentially dominate the film thickness, we can not directly measure them within a given grain boundary. Therefore, as a framework for interpreting the data we consider two appropriate $q_s$ dependent limits; one is dominated by the colligative effect and one is dominated by electrostatic interactions.