Rotation of Water Molecules and Its Relation with the Chemistry and Physics of Liquid Water

2013

ChemPhysChem

An earlier study on the properties of supercooled water and some solutes obtained by simple graphical extrapolation of data available in the literature, determined above the freezing point, led to the hypothesis that water could have a temperature of structural arrest at t0 =-30 °C for H2 O and -22 °C for D2 O. From the present investigation of many more properties of a widely varied nature, this discovery is confirmed throughout. The method is compared with the classical logarithmic Arrhenius and van't Hoff methods that predict t0 always to occur at 0 K, and with the more recently used power law dependence method. With the latter, extrapolated plots intersect the temperature axis at or near to a value of ts =-45 °C, that is, systematically more negative than t0 . It is argued that this ts value, which is the so-called singularity temperature, is likely to be an artefact. It is suggested that, instead of using modified van 't Hoff or Arrhenius relationships to describe temperature dependences in the full temperature range, polynomials in (t-t0 ) should be used.

Section: Direct Graphical Extrapolationmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 75%

Section: Ionic Conductivitymentioning

confidence: 91%

Section: Direct Graphical Extrapolationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Temperature Dependence of the Properties of Water and Its Solutes, Including the Supercooled Region

2013

ChemPhysChem

Arrest as a General Property of the Supercooled Liquid State

2016

J. Phys. Chem. B

Owing to the universal presence of intermolecular interactions, it has to be expected that at some well-defined lower temperature a liquid loses its dynamic properties like fluidity and self-diffusion. As a sequel to two earlier papers on the discovery of such an arrest temperature T0 for supercooled water at 243 K, where also the coexisting vapor pressure was found to become zero, in this paper a further study is undertaken of the behavior of a selection of other liquids. At first, two simple equations of state (van der Waals and virial) are shown in principle to predict a zero vapor pressure at a finite temperature. The interaction parameters B (second virial coefficient) and μJT (Joule-Thomson coefficient) of the vapor are found to become virtually infinite at a temperature T0,B, with a value equal or close to the T0 derived from the liquid properties. Just as earlier found for water, the latter is obtained by extrapolation of several available dynamic and equilibrium data, which should produce an intersection with the temperature axis at the same T0 value. With the exception of molten salts and liquid pure metals, this condition appears to be fulfilled quite accurately. Thus, the temperature of arrest is a general phenomenon for supercooled liquids. As an illustration, it is shown how the PVT diagram of carbon dioxide can be extended into the supercooled temperature region. It is argued that T0 is the temperature below which the Boltzmann energy, kT, is lower than the minimal energy needed for a molecule to break the interactions with its surrounding molecules. We propose to name this minimal energy, kT0, the multimolecular potential of the liquid object. The relationship of the liquid multimolecular potential with the pair potential, ε, of the molecular species is established for various examples and appears to be a proportionality with ε ≈ 2kT0.

Deviation from van’t Hoff Behavior of Solids at Low Temperature

2017

ACS Omega

As a sequel to results obtained on the low-temperature behavior of liquids, a similar study is presented for solids. A molecule in a solid interacts with the other molecules of the crystal so that it is subjected to a specific multimolecular potential, kT0. At temperature T < T0, the molecules are localized, and at T > T0, they can participate in processes like self-diffusion and evaporation. As a consequence, the van’t Hoff equation is disobeyed at a low temperature and properties like vapor pressure, diffusion rate, or reactivity are zero below the specific temperature, T0, which here can be interpreted as a temperature of thermal stability of the solid. To account for this view, the van’t Hoff equation, represented by the green curve in the figure, is extended with a suitable pre-exponential factor, leading to the red curve. Three examples, taken from the literature, are analyzed to demonstrate its applicability. These examples are: the thermal dissociation of calcium carbonate, the sublimation equilibrium pressure of naphthalene, and that of ice. For some other solids, equilibria and dynamic properties, X(T), are examined by means of extrapolations in the X(T) versus T domain, showing the presence of an arrest temperature, which coincides, within experimental accuracy, with the T0 value obtained from the corresponding vapor pressure. As with liquids, kT0 is found to be proportional to the molecular pair potential.