Structural Investigations of Argon Hydrates at Pressures up to 10 kbar

Thermodynamic and Raman Spectroscopic Studies of Ar Hydrate System

“…Those facts strongly support that the structural phase transition in the Ar hydrate crystal occurs around 456 MPa, and that the structure of Ar hydrate observed over 456 MPa (region C) would be structure-H as reported by Manakov, Voronin, Kurnosov, Teplykh, Larionov, and Dyadin [5] and Manakov, V. I. Voronin, A. V. Kurunosov, A. E. Teplykh, V. Y. Komarov, and Y. A. Dyadin [14] and Loveday, Nelmes, Klug, Tse, and Desgreniers [9]. Additionally, in the high-pressure region (760 to 960 MPa), the tetragonal Ar hydrate would be stable as Kurnosov, Manakov, Komarov, Voronin, Teplykh, and Dyadin [7] have reported.…”

“…However, Shimizu, Hori, Kume, and Sasaki [10] have evaluated the multi occupancy of Ar atoms by the Raman spectra of Ar-Ar interatomic stretching vibration around 150 cm -1 . Manakov, Voronin, Kurnosov, Teplykh, Komarov, and Dyadin [14] have suggested the double occupancy of the structure-II Ar hydrate in the pressure region from (340 to 440) MPa based on neutron diffraction experiments at 293 K. Tanaka, Nakatsuka, and Koga [11] reported that double occupancy dominated over single occupancy above 270 MPa from van der Walls Platteuw theory. In the present study, those were not taken up because it was difficult to clarify the meaning Raman peak from noises on the shoulder of Rayleigh scattering.…”

“…The double occupancy of Ar hydrate system has been predicted by many simulation approaches [11][12][13]. Based on the neutron diffraction experiments at 293 K, Manakov, Voronin, Kurnosov, Teplykh, Komarov, and Dyadin [14] have reported the multioccupancy of the structure-II Ar hydrate in the pressure range from (340 to 430) MPa.…”

Monte Carlo study of sII and sH argon hydrates with multiple occupancy of cages

“…Inerbaev et al [20] used first-principle and lattice dynamics calculations to study the electronic, structural, dynamic and thermodynamic properties of Ar hydrate (structures II, H, and tetragonal) considering the effect of multiple-guest molecules in the cages. Manakov et al [21] studied neutron diffraction patterns of argon hydrates at pressures up to 1000 MPa and reported the filling of the large cavities of sH structure by five argon atoms. Ogienko et al [18] reported X-ray diffraction patterns of the sH structure argon hydrate at different temperatures.…”

“…In the future additional guest gases of significant interest such as nitrogen and hydrogen are going to be considered. 21 …”