Mechanism of anisotropic surface self-diffusivity at the prismatic ice-vapor interface.
Predictive theoretical models for mesoscopic roughening of ice require improved understanding of attachment kinetics occurring at the ice-vapor interface. Here, we use classical molecular dynamics to explore the generality and mechanics of a transition from anisotropic to isotropic self-diffusivity on exposed prismatic surfaces. We find that self-diffusion parallel to the crystallographic a-axis is favored over the c-axis at sub-melt temperatures below about -35 °C, for three different representations of the water-water intermolecular potential. In the low-temperature anisotropic regime, diffusion results from interstitial admolecules encountering entropically distinct barriers to diffusion in the two in-plane directions. At higher temperatures, isotropic self-diffusion occurring deeper within the quasi-liquid layer becomes the dominant mechanism, owing to its larger energy of activation.
Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, P.O. 5825, Doha, Qatar. igladich@qf.org.qa.
Ivan
I
Gladich
Amrei
A
Oswald
Natalie
N
Bowens
Sam
S
Naatz
Penny
P
Rowe
Martina
M
Roeselova
Steven
S
Neshyba