Enhanced heating of salty water and ice under microwaves: Molecular dynamics study

TL;DR

This study uses molecular dynamics simulations to explore how microwaves enhance heating in salty ice and water, revealing that salt ions weaken hydrogen bonds, allowing water molecules to rotate more freely and increase heating efficiency.

Contribution

It demonstrates that salt ions weaken hydrogen bonds in ice, enabling more effective microwave heating, with a focus on the electrostatic effects over geometric factors.

Findings

Salt ions weaken hydrogen bonds in salty ice.

Water molecules in salty ice rotate similarly to pure water under microwaves.

Electrostatic effects of salt ions are key to enhanced heating.

Abstract

By molecular dynamics simulations, we have studied the enhanced heating process of salty ice and water by the electric field of applied microwaves at 2.5 GHz, and those in the range 2.5-10 GHz for the frequency dependence. We show that water molecules in salty ice are allowed to rotate in response to the microwave electric field to the extent comparable to those in pure water, because the molecules in salty ice are loosely tied by hydrogen bonds with adjacent molecules unlike the case of rigidly bonded pure ice. The weakening of hydrogen-bonded network of molecules in salty ice is mainly caused by the electrostatic effect of salt ions rather than the short-range geometrical (atom size) effect of salt ions since the presence of salt ions with small radii results in similar enhanced heating.