Speaker
Dr
David Limmer
(Princeton University)
Description
At ambient conditions, water sits close to phase coexistence
with its crystal. More so than in many other materials, this
fact is manifested in the fluctuations that maintain a large
degree of local order in the liquid. These fluctuations and
how they result in long-ranged order, or its absence, are
emergent features of many interacting molecules. Their study
therefore requires using the tools of statistical mechanics
for their systematic understanding. In this talk I present
an overview such an understanding. In particular, I focus on
collective behavior that emerges in liquid and solid water.
At room temperatures, the thermophysical properties of water
are quantified and rationalized with simple molecular
models. A key feature of these models is the correct
characterization of the competition between entropic forces
of packing and the energetic preference for tetrahedral
order. At cold temperatures, the properties of ice surfaces
are studied with statistical field theory. The theory I
develop for the long wavelength features of ice interfaces
allows us to explain the existence of a premelting layer,
the stability of ice in confinement and the dynamical
fragile-to-strong crossover observed in confined water. In
between these extremes, the dynamics of supercooled water
are considered. A detailed theory for the early stages of
coarsening is developed and used to explain the peculiar
observation of a transient second liquid state of water.
When coarsening dynamics are arrested, the result is the
formation of glassy states of water. I show that
out-of-equilibrium the phase diagram for supercooled water
exhibits a rich amount of structure, including a triple
point between two glass phases of water and the liquid.
Using this perspective a number of response properties of
amorphous ice are calculated and compared with experiment.
Throughout all of this work, by invoking only behaviors that
are well established and universal to many other liquids, I
show how the properties of water can be understood without
having to hypothesize the existence of extra features of
water's phase diagram.
