期刊
JOURNAL OF CHEMICAL PHYSICS
卷 129, 期 23, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.3039760
关键词
densification; dielectric relaxation; high-pressure solid-state phase transformations; ice; molecular orientation; permittivity
资金
- Swedish Research Council
- The Faculty of Science and Technology, Umea University
- NSERC's Discovery
Collapse of an ice clathrate of type II structure containing tetrahydrofuran as guest molecules has been studied at different pressures by dielectric spectroscopy. The sample was pressurized to 1.3 GPa at 130 K and the resulting collapsed state was pressure cycled. The dielectric relaxation time increases at a progressively rapid rate during pressurizing and then decreases slowly on depressurizing, but the dielectric relaxation time does not reach the value of the original state. With increase in pressure, the limiting high frequency permittivity due to orientation of H2O molecules first increases by about 5% until 0.75 GPa and then decreases slightly until 1 GPa, and finally it increases until similar to 1.2 GPa. The decrease is attributed to the loss of contribution from the reorientational motion of tetrahydrofuran molecules and the increase to densification as the structure mechanically collapses completely in the 1-1.25 GPa range. The relaxation time of the collapsed state is comparable with that of the high-density amorph formed on pressure collapse of ice.
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