Ultralow elastic stability of salt ice at low temperatures

Abstract

A model is developed to describe the elastic stability of saline ice with a homogeneous distribution of the components in the volume at high pressures (P > 0.1 GPa) and low temperatures (T < 220 K). This model is based on the basic principles of the theory of elastic percolation and the theory of ion hydration (formation of spherical clusters with water molecule dipoles oriented toward ions) in a liquid solution. This model can be used to find the dependence of the elastic stability of an ice solution on the concentration and temperature for any salts decomposing into ions with various valences and effective radii. Good agreement between the calculated and experimental dependences indicates the existence of hydration spheres in an ice solution, which is characterized by a narrower size distribution of spheres as compared to the liquid state and by a steeper decrease in the sphere size when the salt concentration increases in the range x ∼ 0.001–0.01. The stability of a solid ice solution depends on the temperature and the salt concentration in a complicated manner, having specific features in the form of maxima near phase transitions in a water matrix as a result of competing effects that enhance or weaken the elastic contributions of the frozen spheres. As follows from the model calculations, solid ice solutions can have an ultralow elastic stability (which is lower than that of pure water ice by a factor of 5–30), which was experimentally detected even at low weight fractions of salts at a level of x ∼ 0.0001–0.01 for T < 220 K.