The incompressibility and thermal expansivity of D2O ice II determined by powder neutron diffraction

Using high-resolution neutron powder diffraction, the molar volume of a pure sample of D2O ice II has been measured, within its stability field, at 225 K, over the pressure range 0.25 < P < 0.45 GPa. Ar gas was used as the pressure medium, to avoid the formation of 'stuffed ice' gas hydrates encountered when using He. The third-order Birch - Murnaghan equation of state parameters of helium-free D2O ice II, referenced to 225 K, are: V-0,V-225 = 306.95 +/- 0.04 angstrom(3) ( 1299.7 +/- 0.2 kg m(-3)), K-0,K-225 = 12.13 +/- 0.07 GPa, with K'(0.225) fixed at 6.0. The thermal expansivity of metastable D2O ice II samples recovered to ambient pressure has also been measured, over the range 4.2 < T < 160 K; above 160 K an irreversible transition to ice Ic was observed. The volumetric expansion coefficient, alpha(V), at P = 0 and T = 225 K, is predicted to be 2.48 x 10(-4) K-1.