Amazing growth of helium crystal facets

Abstract

ÍÑÕÑÓÂâ ³ÒËÔÑÍ ÎËÕÇÓÂÕÖÓÞ This review systematizes the experimental data from the study of two unusual phenomena: the super-slow growth of a perfect, growthdefect-free crystal facet, and the abrupt transition of a crystal facet to an abnormal state at a growth rate two to three orders of magnitude greater than the normal value (the effect of "burst-like growth").

Shock growth of ice crystal near equilibrium melting pressure under dynamic compression

“…Then, the growth speed increases by an order of magnitude under fast compression, accompanying the morphological transition. While a burst-like or rapid growth behavior has been reported for helium crystal (14–16), organic glasses (34), and colloidal crystals (22, 23), the dimensional transition from 3D to 2D crystal has never been observed as a function of compression rate. The dramatic changes in both morphology and growth speed imply that the local equilibrium growth condition at the crystal–liquid interface is severely disturbed by the fast compression, and thus large driving force (i.e., overpressure) may be applied.…”

“…Therefore, the fast compression yields effectively large overpressure ahead of the crystal edge plane until building the enhanced interface structure. This scenario may be applied to explain anomalous growth behaviors by cooling rate (12, 13) or abrupt pressure change (14–16) near equilibrium melting temperature or pressure, which have waited to be resolved.…”

“…In general, the crystal growth and morphology are mainly determined by an interplay between macroscopic thermodynamic driving forces and microscopic kinetic process taking place at a crystal–liquid interface. While the crystal growth is well understood near local-equilibrium growth condition in terms of the interplay (7–11), the formation and transition of diverse crystal morphologies remain poorly understood under local non- or far-from-equilibrium growth conditions, such as zigzag growth in 2D (12, 13), rapid or burst-like growth of helium crystal (14–16), ice crystals (17), and alloys (18). These anomalous growth behaviors imply that the local equilibrium condition at the crystal–liquid interface is disturbed by sudden application of a large driving force.…”

“…These anomalous growth behaviors imply that the local equilibrium condition at the crystal–liquid interface is disturbed by sudden application of a large driving force. While theoretical (19–21) and simulation (22, 23) studies have reported that both the interface kinetics and the thermodynamic driving forces indeed play a key role in morphological transitions and anomalously fast growth under nonequilibrium conditions, many experimental discoveries remain unexplained due to technical challenges of accessing the local nonequilibrium or far-from-equilibrium conditions on a consistent basis (9, 12–18). This is particularly true for applying the rate-dependent driving force, like cooling rate (13), yielding large driving force, since it evidently accompanies inherent thermal or concentration gradient due to the thermal and mass transport phenomena, causing time delay and spatial inhomogeneity of the physical events during experimental procedures.…”

“…Recently, intensive interest in pressure-induced crystal nucleation and growth has emerged in the fields of static- (14–16, 24–26) and dynamic compression (i.e., shock compression) (17, 27–32). Remarkably, the application of dynamic pressure could generate unexpected crystal growth behaviors, such as burst-like and oscillation growths in helium crystal with small overpressure even near equilibrium melting pressure (14–16). Moreover, a high compression rate changes ice crystal morphology from 3D to 2D with anomalously fast growth, and facet to dendritic growth (17).…”