An international group of scientists from the United States and Canada revealed anomalous properties of amorphous ice formed at extremely low temperatures and high pressure. It was considered that this phase is directly linked to liquid water, which helped to explain some anomalous properties of the latter, however, the new results showed that it is not. This publication reports Science Alert.
The researchers tried to obtain amorphous ice, freezing sphere of heavy water with a diameter of three millimeters at a temperature of minus 173 degrees Celsius and gradually increasing the pressure up to 28 thousand atmospheres. However, instead of the desired phase they received passing each other crystal modifications. First they formed regular ice with hexagonal structure, then the ice IX, ice XV and finally, ice XIII.
It was found that the amorphous form is formed instead of ice IX only when a rapid pressure increase. In this case, the usual ice can’t turn to ice XV. Thus, the formation of amorphous ice is actually a consequence of the termination of the transformation between the two crystalline modifications, which casts doubt on the current theory.
Amorphous ice has three varieties. One of them is amorphous ice, high density (HDA) is obtained from ordinary ice at a pressure of 11 atmospheres and a temperature of less than minus 143 degrees Celsius. The process of getting HDA is described as a thermodynamic melting, it is considered that this phase is a glassy state of water.
Thanks to the ability to reversibly transform to HDA amorphous ice low-density, researchers have developed a two-fluid model, according to which each form of amorphous ice is associated with one of the two components of liquid water (normal and superfluid). This could explain some anomalous properties of the liquid phase related to the density and heat capacity.
Video, photo All from Russia.