Neutron scattering by heavy water and ice under hydrostatic pressure of argon

The neutron diffraction study of the system argon-heavy water under pressures of 100 and 300 MPa revealed the formation of clathrate argon hydrate (type II structure, sp. gr.Fd3-barm,a=17.167 A at 283 K) and the corresponding modifications of ice (ice Ih at 100 MPa and ice II at 300 MPa). The neutron diffraction patterns and the spectra of inelastic incoherent neutron scattering were obtained at temperatures up to 190 K. Possible penetration of argon into the cavities of the crystal structure of ice II is discussed. However, the available experimental data are insufficient for either the confirmation of this assumption or for the determination of void occupancies with argon in this clathrate hydrate