Enthalpy Relaxation Phenomenon of Heavy Ice

Abstract

The heat capacities of quenched and annealed heavy ice Ih were measured in the temperature range 14 to 300 K by an adiabatic calorimeter. A relaxational thermal anomaly was found at around 115K and this phenomenon was ascribed to the onset of deuteron ordering in the crystal. The average activation enthalpy of the relaxational process was determined to be (26±5) kJ mol–1. Residual entropies of the crystal were recalculated on the basis of the present heat-capacity data combined with the revised values for enthalpy of vapourization, saturated vapour pressure, and spectroscopic entropy. They are (3.47±0.41) J K–1 mol–1 for the quenched crystal and (3.44±0.41) J K–1 mol–1 for the crystal annealed at 102–106 K for 264 h. The characteristics and the origin of the anomaly are discussed in comparison with that of ordinary ice.

Accurate and precise lattice parameters of H2O and D2O ice Ihbetween 1.6 and 270 K from high-resolution time-of-flight neutron powder diffraction data

“…There are numerous reports of 'anomalous' behaviour in ice in the vicinity of 100-150 K from a variety of physical measurements including dielectric properties (Dengel et al, 1964;Chamberlain & Fletcher, 1971;Johari & Jones, 1975, the specific heat (Beukel, 1968;Haida et al, 1973Haida et al, , 1974Haida et al, , 1979, the elastic constants (Helmreich & Bullemer, 1969;Ermolieff, 1975), and the scattering of -rays (Fitzgerald & O'Connor, 1976). These anomalies were, in many cases shown to be dependent on the thermal history of the sample (i.e.…”

The adsorption and desorption of ethanol ices from a model grain surface

“…2 is probably due to a change in ethanol orientation for exposures above 20 L. The base temperature of the HOPG substrate ͑98 K͒ is very close to that of the glass transition temperature of amorphous ethanol ͑97 K͒ obtained from calorimetric studies. 40 This would suggest that upon adsorption, ethanol may form a viscous liquid phase on the HOPG surface. Hence, the ethanol molecule is sufficiently thermalized upon adsorption to permit a more energetically favorable bonding orientation on the surface.…”

Structural manifestation of partial proton ordering and defect mobility in ice Ih

“…It is straightforward to eliminate the first possibility. ; [13][14][15][16] hence, the most optimistic estimate of S from unquenching of orientational defects is too small by almost a factor of 10 3 . We should be conscious of the fact that it is much more likely for the structural parameter to become frozen in between 200 and 150 K, so the more plausible changes in concentration and thermodynamic quantities will be between 4 and 10 orders of magnitude smaller than those given above.…”

“…Relaxation times in H2O and D2O ice as a function of T. 15,16,23,33,35,36,[38][39][40] The bold dashed red lines bounding the spread of low-T data depict activation energies due to orientational defects (EA = 59 kJ mol −1 , 0 = 1.50x10 −16 s) and ionic defects (EA = 20 kJ mol −1 , 0 = 2.20x10 −8 s). Finer dotted lines show different values of the parameter 'p' (in black) proposed by Popov et al 44 to characterise the resistance to defect migration from correlated movement of orientational and ionic defects.…”

“…A variety of studies provide both experimental and computational evidence for partial ordering of ice Ih far above the transition to ice XI. Calorimetry [13][14][15][16] reveals a fractional decrease in the configurational entropy on cooling that -in a geometricallyconstrained system -can only be the result of partial ordering. 17 Likewise, measurements of the librational peak widths in FTIR studies of ice, and changes in the structure of the librational bands from inelastic neutron spectra both suggest the onset of proton ordering, certainly below 150 K and perhaps as high as 237 K. 18,19 Evidence that ice XI grows more readily from ice Ih that has formed by back-transformation of a preceding generation of ice XI has been interpreted as being due to 'nanodomains' of short-range order persisting some tens of Kelvin above the ice XI → ice Ih transition.…”