jz6b01013_si_001.pdf (1.84 MB)
Microscopic Mechanism and Kinetics of Ice Formation at Complex Interfaces: Zooming in on Kaolinite
journal contribution
posted on 2016-06-06, 00:00 authored by Gabriele C. Sosso, Tianshu Li, Davide Donadio, Gareth
A. Tribello, Angelos MichaelidesMost
ice in nature forms because of impurities which boost the
exceedingly low nucleation rate of pure supercooled water. However,
the microscopic details of ice nucleation on these substances remain
largely unknown. Here, we have unraveled the molecular mechanism and
the kinetics of ice formation on kaolinite, a clay mineral playing
a key role in climate science. We find that the formation of ice at
strong supercooling in the presence of this clay is about 20 orders
of magnitude faster than homogeneous freezing. The critical nucleus
is substantially smaller than that found for homogeneous nucleation
and, in contrast to the predictions of classical nucleation theory
(CNT), it has a strong two-dimensional character. Nonetheless, we
show that CNT describes correctly the formation of ice at this complex
interface. Kaolinite also promotes the exclusive nucleation of hexagonal
ice, as opposed to homogeneous freezing where a mixture of cubic and
hexagonal polytypes is observed.