High density amorphous ices: disordered water towards close packing.
The structure of amorphous ice under pressure has been studied by molecular dynamics at 160 K. The starting low-density phase undergoes significant changes as the density increases, and at rho=1.51 g/cm(3) our calculated g(OO)(r) is in excellent agreement with in situ neutron diffraction data obtained at 1.8 GPa and 100 K on very high density amorphous ice made at 150 K. As the system is further compressed, in the theoretical simulations, up to rho=1.90 g/cm(3), the structural modifications are continuous up to the highest density. The analysis of orientational distributions reveals that dense amorphous ice is characterized by major distortions of the tetrahedral geometry, and that the pressure structural changes, already observed experimentally at lower densities, can be interpreted as a trend towards a disordered closed-packed structure.
Saitta
A Marco
AM
Physique des Milieux Condensés, CNRS-UMR 7602, B77, Université Pierre et Marie Curie, F-75252 Paris, France. ms@pmc.jussieu.fr
Strässle
Thierry
T
Rousse
Gwenaëlle
G
Hamel
Gérard
G
Klotz
Stefan
S
Nelmes
Richard J
RJ
Loveday
John S
JS