Analysis of the effect of water activity on ice formation using a new thermodynamic framework

Barahona, D.

doi:10.5194/acp-14-7665-2014

Cited by 21 publications

(51 citation statements)

References 58 publications

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“…Recent MD simulations showing the existence of a low-density region around the ice germ support the NNF model (Singh and Bagchi, 2014). Introducing NNF into CNT and correcting the nucleation work for mixing effects resulted in good agreement of predicted J hom with experimental results (Barahona, 2014). NNF was also shown to be consistent with the water activity criterion.…”

Section: Introductionsupporting

confidence: 52%

“…MD results, however, suggest that the properties of water in the vicinity of the ice germ differ from the bulk, casting doubt on such an approach (e.g., Kawasaki and Tanaka, 2010;Singh and Bagchi, 2014). Unlike for the interfacial energy where several theoretical models have been proposed (e.g., Spaepen, 1975;Digilov, 2004;Barahona, 2014), the theoretical treatment of G act has been limited. One possible reason is that interface transfer is associated with random fluctuations near the ice-liquid interface and is therefore difficult to treat in terms of macroscopic variables.…”

Section: Introductionmentioning

confidence: 98%

“…CNT provides a framework to understand ice nucleation and has been instrumental in the development of parameterizations from experimental data (e.g., Pruppacher and Klett, 1997;Khvorostyanov and Curry, 2009;Murray et al, 2010). On the other hand, J hom estimated with CNT and using independent estimates of thermodynamic parameters typically results in stark disagreement with measurements (Pruppacher and Klett, 1997;Kawasaki and Tanaka, 2010;Barahona, 2014). Thus, CNT is commonly used semiempirically, fitting several parameters of the theory, most commonly the liquidice interfacial tension, σ iw , and the activation energy, G act , to measured nucleation rates (e.g., Jeffery and Austin, 1997;Khvorostyanov and Curry, 2004;Murray et al, 2010;Ickes et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

“…It has been shown that σ iw obtained by fitting CNT to measured nucleation rates tends to be biased high to account for mixing effects neglected in common formulations of CNT (Barahona, 2014). Moreover, the dependency of σ iw on temperature tends to depend on the value of other fitted parameters of the theory (Ickes et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the dependency of σ iw on temperature tends to depend on the value of other fitted parameters of the theory (Ickes et al, 2015). Recently, Barahona (2014) (hereinafter B14) introduced a mechanistic model of the ice-liquid interface in terms of thermodynamic variables, without fitting CNT to measured nucleation rates. This was done by hypothesizing the existence of a transition layer around the ice germ, with chemical potential defined by the entropy of the ice and the enthalpy of the liquid, and using the model of Spaepen (1975) to define the interface thickness.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamic derivation of the activation energy for ice nucleation

Barahona

2015

Atmos. Chem. Phys.

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Abstract. Cirrus clouds play a key role in the radiative and hydrological balance of the upper troposphere. Their correct representation in atmospheric models requires an understanding of the microscopic processes leading to ice nucleation. A key parameter in the theoretical description of ice nucleation is the activation energy, which controls the flux of water molecules from the bulk of the liquid to the solid during the early stages of ice formation. In most studies it is estimated by direct association with the bulk properties of water, typically viscosity and self-diffusivity. As the environment in the ice-liquid interface may differ from that of the bulk, this approach may introduce bias in calculated nucleation rates. In this work a theoretical model is proposed to describe the transfer of water molecules across the ice-liquid interface. Within this framework the activation energy naturally emerges from the combination of the energy required to break hydrogen bonds in the liquid, i.e., the bulk diffusion process, and the work dissipated from the molecular rearrangement of water molecules within the ice-liquid interface. The new expression is introduced into a generalized form of classical nucleation theory. Even though no nucleation rate measurements are used to fit any of the parameters of the theory the predicted nucleation rate is in good agreement with experimental results, even at temperature as low as 190 K, where it tends to be underestimated by most models. It is shown that the activation energy has a strong dependency on temperature and a weak dependency on water activity. Such dependencies are masked by thermodynamic effects at temperatures typical of homogeneous freezing of cloud droplets; however, they may affect the formation of ice in haze aerosol particles. The new model provides an independent estimation of the activation energy and the homogeneous ice nucleation rate, and it may help to improve the interpretation of experimental results and the development of parameterizations for cloud formation.

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Section: Introductionsupporting

confidence: 52%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermodynamic derivation of the activation energy for ice nucleation

Barahona

2015

Atmos. Chem. Phys.

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Study on ice nucleation temperature and water freezing in saline soils

Wan

Liu

Qiu

2020

Permafrost & Periglacial

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This paper presents a computational model of the freezing point of soil and the nucleation rate of ice based on the soil volume for saline soils. Physicochemical methods and crystallization theory are used to explore the macroscopic mechanism of water freezing induced by ice crystallization, and the influence of water undercooling is discussed with regard to different soil volumes and salt contents. Growth sites, shapes, and sizes of ice crystals are determined by an assumption of heterogeneous nucleation, and the contact angle is introduced to represent a wide range of soils. The relationship between the initial contact angle and the salt content is analyzed quantitatively through an indoor cooling test and thermal difference analysis. Moreover, the van Genuchten model is applied to provide an equation for the unfrozen water content in salty soils, and the probability of ice formation is introduced to investigate the variation of contact angle during the soil freezing process. This study shows that the initial radius of an ice crystal decreases as the salt concentration decreases. The temperature of ice nucleation is determined mainly by the contact angle of ice crystals, which decreases as the soil volume increases and results in decreased supercooling.

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