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The microscopic features of heterogeneous ice nucleation may affect the macroscopic morphology of atmospheric ice crystals

Cox, SJ; Raza, Z; Kathmann, SM; Slater, B; Michaelides, A; (2013) The microscopic features of heterogeneous ice nucleation may affect the macroscopic morphology of atmospheric ice crystals. FARADAY DISCUSSIONS , 167 389 - 403. 10.1039/c3fd00059a. Green open access

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Abstract

It is surprisingly difficult to freeze water. Almost all ice that forms under “mild” conditions (temperatures > −40 °C) requires the presence of a nucleating agent – a solid particle that facilitates the freezing process – such as clay mineral dust, soot or bacteria. In a computer simulation, the presence of such ice nucleating agents does not necessarily alleviate the difficulties associated with forming ice on accessible timescales. Nevertheless, in this work we present results from molecular dynamics simulations in which we systematically compare homogeneous and heterogeneous ice nucleation, using the atmospherically important clay mineral kaolinite as our model ice nucleating agent. From our simulations, we do indeed find that kaolinite is an excellent ice nucleating agent but that contrary to conventional thought, non-basal faces of ice can nucleate at the basal face of kaolinite. We see that in the liquid phase, the kaolinite surface has a drastic effect on the density profile of water, with water forming a dense, tightly bound first contact layer. Monitoring the time evolution of the water density reveals that changes away from the interface may play an important role in the nucleation mechanism. The findings from this work suggest that heterogeneous ice nucleating agents may not only enhance the ice nucleation rate, but also alter the macroscopic structure of the ice crystals that form.

Type: Article
Title: The microscopic features of heterogeneous ice nucleation may affect the macroscopic morphology of atmospheric ice crystals
Open access status: An open access version is available from UCL Discovery
DOI: 10.1039/c3fd00059a
Publisher version: http://dx.doi.org/10.1039/c3fd00059a
Additional information: © The Royal Society of Chemistry 2013. This Open Access Article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/1423689
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