Surfaces of Ice

Dynamic phase transitions at the ice surfaces and interfaces occur in association with and in connection with the structures of ice surfaces and interfaces rather than the bulk properties of ice and especially with the dynamic behavior of phase transitions during growing and melting of ice crystals. Consequently, research on ice 

Surface and Interface Science Properties of Composite Surfaces Alloys, Compounds, Semiconductors, 

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Liquid interfaces are widely found in nature as a substrate for chemical reactions. This is rather obvious in biology, but even in the diluted stratospheric conditions, many reactions occur at interfaces like the surface of ice crystallites. The number of techniques available to carry out these studies is, however, limited and this is particularly true in optics, since linear optical methods do not possess the ultimate molecular resolution. This resolution is inherent to nonlinear optical processes of even order. For liquid-liquid systems, optics turns out to be rather powerful owing to the possibility of nondestructive y investigating buried interfaces. Furthermore, it appears that planar interfaces are not the only config-... 

We say something is as slippery as an ice rink if it is has a tiny coefficient of friction, and we cannot get a grip underfoot. This is odd because the coefficient of friction /r for ice is quite high - try dragging a fingernail along the surface of some ice fresh from the ice box. It requires quite a lot of effort (and hence work) for a body to move over the surface of ice. 

You now have enough experience with DFT calculations to imagine how calculations could be performed that would be relevant for each of the three examples listed above. For instance, DFT calculations could be used to determine the relative energy of various kinds of lattice defects that could potentially exist in a solid material. Similar calculations could be used to determine the equilibrium positions of reactive molecules on the surfaces of ice crystals that could be thought of as mimics for polar stratospheric clouds. 

The presence of ionizing radiation in the upper regions of the earth s atmosphere and the realization that atmospheric chemistry can occur on the surface of ice and dust particles have lead many authors to study on the interaction of LEE with molecular solids of ozone [203], HCl [236], and halogen-containing organic compounds [176,177,195-197,199-202,205,214,217,224-234] in an effort to shed new light on the problem of ozone depletion. In a recent series of experiments, Lu and Madey [297,298] found that the and CG yields... 

Abstract Heterogeneous chemical reactions at the surface of ice and other stratospheric aerosols are now appreciated to play a critical role in atmospheric ozone depletion. A brief summary of our theoretical work on the reaction of chlorine nitrate and hydrogen chloride on ice is given to highlight the characteristics of such heterogeneous mechanisms and to emphasize the special challenges involved in the realistic theoretical treatment of such reactions. 

The discovery of the Ozone Hole in the Antarctic stratosphere has led to the realization that previously unsuspected heterogeneous chemical reactions occuring on the surface of ice and other stratospheric cloud particles play a critical role in atmospheric ozone depletion — not only in the Antarctic stratosphere,... 

FIGURE 12.24 Schematic of the incorporation of HCl from the gas phase onto the surface of ice via hydrogen bonding, followed by condensation of water and ionization of the HCl (adapted from Gertner and Hynes, f 996). 

Tabazadeh, A., and R. P. Turco, A Model for Heterogeneous Chemical Processes on the Surfaces of Ice and Nitric Acid Trihydrate Particles, J. Geophys. Res., 98, 12727-12740(1993). 

When a solute is present in water, the solute takes up space and decreases the number of liquid molecules at the liquid—solid interface. The space taken up by solute molecules decreases the probability of a water molecule adhering to the surface of ice and raising the overall freezing point of water. 

Reaction (1) is known to proceed relatively rapidly on the surface of ice under acidic conditions,9-12 and one such acidic condition could be realized via ionic dissociation of HC1, i.e. a proton transfer from molecular HC1 to a coordinated water molecule to form a CrH30+ contact ion pair (CIP) in the... 

Atomic hydrogen is only weakly adsorbed on the surfaces of ice and paraffins. There is, nevertheless some adsorption on these surfaces at very low temperatures, and a combination reaction... 

Molecules interact with the surfaces of solids in almost every environment in the universe. In addition to purely intellectual interest, we customarily justify studying these interactions on technological grounds, heterogeneous catalysis and the fabrication of microchips being the most frequently listed applications. However the field is much more broadly relevant the adsorption and desorption of atoms and molecules on the surfaces of dust grains is very important to molecule formation in the interstellar medium, reactions on the surfaces of ice crystals is important in atmospheric chemistry and reactions at surfaces determine the behaviour of medical implants in our bodies. 

Dry air at 25°C and atmospheric pressure blows over a 30-cm-square surface of ice at a velocity of 1.5 m/s. Estimate the amount of moisture evaporated per hour, assuming that the block of ice is perfectly insulated except for the surface exposed to the airstream. 

For our studies we used a commercial Atomic Force Microscope (PicoSPM, Molecular Imaging) as it provided a large open access area for installing the low-temperature sample environment. Several technical problems needed to be solved before we could investigate the surface of ice in air at temperatures down to -35°C. 

In the course of one AFM experiment, after the measurement at 5% relative humidity, we increased the relative humidity of the environment up to 50% during 1 min. The increase of the relative humidity led to the formation of delicate frost on the flat surface of ice (Fig.4a). These individual frost crystals disappeared within a few minutes of scanning (Fig.4b and 4c) and from them remained just a few residuals (Fig.4c). It is however not clear whether the crystals were removed, crushed or melted by the AFM tip. 

Finally, these results also show that at 90 K all the HCl molecules adsorbed on the surface of ice are dissociated. 

A sample consisting of packed ice particles has numerous cavities and ice particle surfaces inside, and the number of dangling bonds oriented with a hydrogen nucleus at the surface of ice tends to increase. Therefore we can expect that the number of L-defects near the ice particle surfaces also tends to increase and protons near the ice particle surface can easily move. The dispersion of the Davidson-Cole type may be caused by proton behaviors near the ice particle surfaces in a sample consisting of packed ice. 

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