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Abstract Cirrus ice crystals are produced heterogeneously on ice‐nucleating particles (INPs) and homogeneously in supercooled liquid solution droplets. They grow by uptake of water molecules from the ice‐supersaturated vapor. The precursor particles, characterized by disparate ice nucleation abilities and number concentrations, compete for available vapor during ice formation events. We investigate cirrus formation events systematically in different temperature and updraft regimes, and for different INP number concentrations and time‐independent nucleation efficiencies. We consider vertical air motion variability due to mesoscale gravity waves and effects of supersaturation‐dependent deposition coefficients for water molecules on ice surfaces. We analyze ice crystal properties to better understand the dynamics of competing nucleation processes. We study the reduction of ice crystal numbers produced by homogeneous freezing due to INPs in both, individual simulations assuming constant updraft speeds and in ensemble simulations based on a stochastic representation of vertical wind speed fluctuations. We simulate and interpret probability distributions of total nucleated ice crystal number concentrations, showing signatures of homogeneous and heterogeneous nucleation. At typically observed, mean updraft speeds (≈15 cm s−1) competing nucleation should occur frequently, even at rather low INP number concentrations (<10 L−1). INPs increase cirrus occurrence and may alter cirrus microphysical properties without entirely suppressing homogeneous freezing events. We suggest to improve ice growth models, especially for low cirrus temperatures (<220 K) and low ice supersaturation (<0.3).
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Emulsification of Supersaturated Solutions Amplifies Induction Time Variation in Crystallization
The induction time for the onset of nucleation is known to decrease with increasing solution supersaturation. A large variation in induction time is experimentally observed for various organic crystals, whose origin is often associated with the stochastic nature of the nucleation process. Although several empirical models for induction time and nucleation rate have been developed, they remained highly unreliable, with model predictions differing by orders of magnitude from experimental measurements. A satisfactory explanation for the induction time variation has not been developed yet. We report here that the variations in induction times can be attributed to a previously unrecognized consequence of the phase separation or emulsification of supersaturated solution, in addition to the effect of stochastic nucleation. A large-scale Brownian dynamics simulation of antisolvent crystallization of histidine in a water–ethanol mixture is performed to demonstrate the mechanism of microphase/emulsion formation in supersaturated solutions and its consequence on induction time variation. Furthermore, we show that the average induction time depends on supersaturation, and the supersaturation-dependent diffusion of histidine molecules governs the stochastic nature of the induction time. Moreover, at varying supersaturations, the likelihood of forming stable and metastable polymorphs of histidine was estimated. This approach provides valuable insights into the crystallization behavior of histidine, and predicted induction time reasonably matches the experimentally observed induction time.
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- Award ID(s):
- 2132022
- PAR ID:
- 10537220
- Editor(s):
- Steed, Jonathan W
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Crystal Growth & Design
- Volume:
- 23
- Issue:
- 9
- ISSN:
- 1528-7483
- Page Range / eLocation ID:
- 6290 to 6297
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.cgd.3c00051
