Morphological Study of Ice Crystal Growth

Abstract

The morphologies and growth rates of ice crystals have been observed and documented using a novel experiment, with the goal of investigating the overarching principles of the molecular dynamics of ice crystal growth. The experimental set-up consists of two side-by-side temperature-regulated diffusion chambers. Thin ice needles, up to several millimeters in length and a few microns in diameter, are grown in the first chamber off of a metal wire through nucleation caused by the application of a high voltage. These electric needles are then transferred to the second chamber with a controllable internal water vapor supersaturation level, and subsequent growth of the ice crystals is observed. The crystal morphology is captured digitally via optical microscopy and is analyzed in the form of time-stamped images. Varying the supersaturation and overall temperature affects the crystal morphology as well as growth rate and yields insights into the basic physical principles governing crystal growth. A theory that proposes to explain the resulting morphology of ice crystals due to variations in temperature and supersaturation conditions suggests that relative growth rates of the principal facets of a crystal depend on the current morphology of the crystal and on an instability. Computer simulations of this proposed theory called the Structure-Dependent Attachment Kinetics model are tested against real ice crystals to determine the accuracy of the proposed theory.