Liquid State of Low-Density Pressure-Amorphized Ice above Its Tg

Experiments using a blunted conical indentor show that the low-density amorphous solid form of pressure-amorphized ice deforms under load and behaves like a viscous liquid near 143 K, much before its rapid crystallization to cubic ice. Since a mechanical stress biases the molecular diffusion of a fluid undergoing a Newtonian deformation, the observation puts into question the basis for an earlier [ J. Phys. Chem. 1995, 99, 11584] conclusion that water near 140 K is no more fluid than cubic ice. It is pointed out that the profile of the dielectric relaxation rate−temperature plot of supercooled water seriously disagrees with that of the computer-simulated diffusion coefficient in the 206−284 K range (0.966−0.984 g/mL density) and that there is an unusually large discrepancy between the recently determined diffusion coefficient of a 33 molecule thick layer of water at 155 K and the value deduced from the equation obtained from computer simulation.