(412c) Shear-Thinning Behavior of Supercooled Water inside Small Nanotubes and Shear Effect on the Tetrahedral Structure

Water has many unusual properties under bulk conditions. Thus, the question is whether such unusual properties also hold in confined media, and in particular, in nanotubes with small diameters. An important problem is the behavior of water in confined media below the bulk freezing point of 273 K. The problem is relevant to a variety of biological phenomena. We have shown^{1, 2} that water in small nanotubes does not freeze, even at temperatures well below 273 K. Using extensive molecular dynamics (MD) simulations, we show in this study that under the same conditions water is not a Newtonian fluid, but behaves as a shear-thinning one. We compute temperature- and shear-rate dependence of the shear stress and apparent viscosity of water over the temperature range 230 K - 270 K. We also show that as the shear stress increases, the tetrahedrality of water molecules also increases.