Phase transitions and equilibrium hydrogen content of phases in the water-hydrogen system at pressures to 1.8 kbar

摘要

Using a volumetric technique, the hydrogen solubility X in liquid water (L), low-pressure hexagonal ice (I{sub}h), and high-pressure cubic clathrate ice (sII) is studied at hydrogen pressures up to 1.8 kbar and temperatures from -36 to +20 ℃. The triple point of the L + I{sub}h + sII equilibrium is located at P = 1.07(5) kbar and T = -10(1) ℃. The hydrogen concentrations of phases at the triple point are X{sub}L = 0.17(5), X{sub}(I{sub}h) = 0.10(5) and X{sub}(sII) = 2.3(1) wt.% H{sub}2. The thermal stability and the process of decomposition of the clathrate phase at ambient pressure are studied by neutron diffraction.