Amorphous ices molecular structure

More recently, simulation studies focused on surface melting [198] and on the molecular-scale growth kinetics and its anisotropy at ice-water interfaces [199-204]. Essmann and Geiger [202] compared the simulated structure of vapor-deposited amorphous ice with neutron scattering data and found that the simulated structure is between the structures of high and low density amorphous ice. Nada and Furukawa [204] observed different growth mechanisms for different surfaces, namely layer-by-layer growth kinetics for the basal face and what the authors call a collected-molecule process for the prismatic system. 

When partially hydrated samples are cooled down to 77 K, no crystallization peak is detected by differential thermal analysis. The x-ray and neutrons show that an amorphous form is obtained and its structure is different from those of low-and high-density amorphous ices already known [5]. Samples with lower levels of hydration corresponding to one monolayer coverage of water molecules are under investigation. This phenomenon looks similar in both hydrophilic and hydrophobic model systems. However, in order to characterize more precisely the nature of the amorphous phase, the site-site partial correlation functions need to be experimentally obtained and compared with those deduced from molecular dynamic simulations. 

It is well known that irradiation alters the structure of ice. It is amorphized at T < 80 K by protons, ions, photons and electrons. The structures of the irradiated ices have only been determined in the case of intense electron irradiation, where the high-density amorph was detected. Recent molecular dynamic simulations have also shown a densification of the ASW ice when irradiated with 35 eV water molecules,but these simulations also questioned the existence of the high-density phase as the initial structure of ice films deposited at low temperature. 

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