(303d) Heterogeneous Ice Nucleation and Growth: What Effects Do Surfaces Have?

Understanding the role played by solid surfaces in ice nucleation is a significant step toward designing anti-icing surfaces.  Materials that control ice accumulation are important to aircraft efficiency, atmospheric ice nucleation, highway and power line maintenance, building construction, and telecommunication equipment maintenance. Most current deicing systems include either physical or chemical removal of ice; both are energy and resource-intensive. A more desirable approach would be to prevent ice formation rather than to fight its build-up.  The question becomes what about a surface must be tuned to systematically design “ice-phobic” surfaces that are resistant to icing.  Our overall goal is to explain the mechanisms through which surfaces affect ice nucleation and growth and develop predictive abilities to correlate surface properties to likelihood of ice nucleation. In this work, we use microsecond long molecular dynamics (MD) to study ice nucleation near mineral surfaces. As kaolinite is the most abundant mineral dust in the atmosphere that has been shown to promote ice nucleation, we use it as a template surface for our study. We investigate the effect of lattice spacing, surface hydroxyl flexibility and simulation system size on water structure and ice nucleation behavior.  Our studies indicate that in addition to lattice matching, the hydrogen bonding ability of the surface also plays an important role in templating ice structure. Interestingly, ice nucleation in our systems only occurs on surfaces where the lattice spacing of the surface matches the lattice spacing of ice, and for specific orientations of the surface hydroxyl groups. The growth of ice on these surfaces proceeds through a cooperative growth between water layers.  This is different from the layer-by-layer growth observed in silver iodide (AgI, another very efficient ice nucleating agent) surfaces. We will present detailed analysis of water structure and dynamics near the different surfaces that elucidate the correlations between interfacial water structure and likelihood of observing ice nucleation.