This monograph reviews our current understanding of the physical dynamics of ice crystal growth, focusing on the spontaneous formation of complex structures from water vapor (called snow crystals) as a function of temperature, supersaturation, background gas pressure, and other extrinsic parameters. Snow crystal growth is a remarkably rich and rather poorly understood phenomenon, requiring a synthesis of concepts from materials science, crystal-growth theory, statistical mechanics, diffusion-limited solidification, finite-element modeling, and molecular surface processes. Building upon recent advances in precision measurement techniques, computation modeling methods, and molecular dynamics simulations of crystalline surfaces, I believe we are moving rapidly toward the long-sought goal of developing a full physical model of snow crystal formation, using ab initio molecular dynamics simulations to create a semi-empirical characterization of the nanoscale surface attachment kinetics, and then incorporating that into a full computational model that reproduces the growth of macroscopic crystalline structures. Section 1 of this monograph deals mainly with the material properties of ice Ih in equilibrium, including thermodynamics quantities, facet surface structures, terrace step energies, and crystal twinning behaviors.
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