High-density amorphous ice

Amorphous water (also called glassy water or amorphous ice) can form when the temperature is decreased extremely rapidly below the glass transition temperature (Tg) of water (about 130 K at 0.1 MPa) (Mishima and Stanley, 1998). There are three types of amorphous ice low-density amorphous ice (LDA), high-density amorphous ice (HDA), and very high-density amorphous ice (VHDA), with VHDA being discovered most recently (Finney et al., 2002). 

Low-Density Amorphous Ice (LDA). Upon heating HDA to T > 115 K or very high density amorphous ice (VHDA) to T > 125 K at ambient pressure, the structurally distinct amorphous state LDA is produced. Alternatively, LDA can also be produced by decompressing HDA or VHDA in the narrow temperature range of 139-140 K to ambient pressure [153-155]. The density of this amorphous state at 77 K and 1 bar is 0.93 g/cm3 [152]. These amorphous-amorphous transitions are discussed in Sections III.C and III.D. 

Very High Density Amorphous Ice (VHDA). By annealing HDA to T > 160 K at pressures > 0.8 GPa, a state structurally distinct from HDA can be produced, which is called VHDA ice [152]. The structural change of HDA to a distinct state by pressure annealing was first noticed in 2001 [152]. Even though VHDA was produced in experiments prior to 2001 [170], the structural difference and the density difference of about 10% at 77 K, and 1 bar in comparison with HDA remained unnoticed. Powder X-ray diffraction, flotation, Raman spectroscopy, [152] neutron diffraction [171], and in situ densitometry [172, 173] were employed to show that VHDA is a structural state distinct from HDA. Alternatively, VHDA can be prepared by pressurization of LDA to P > 1.1 GPa at 125 K [173, 174] or by pressure-induced amorphization of hexagonal ice at temperatures 130 K < T < 150 K [170]. The density of this amorphous state at 77 K and 1 bar is 1.26 g/cm3 [152]. 

Giovambattista N, Stanley HE, Sciortino E. Phase diagram of 62. amorphous solid water Low-density, high-density and very-high-density amorphous ices. Phys. Rev. E 2005 72 031510. 

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. 

Loerting, T., Salzmann, C., Kohl, I., Mayer, E., and Hallbrucker, A. A second distinct structural "state" of high-density amorphous ice at 77 K and 1 bar, Phys. Chem. Chem. Phys., 3,5355, 2001. 

II. Pressure-Induced Amorphization of Hexagonal Ice High-Density Amorphous Ice (HDA)... 

IV. Apparent First-Order Transition Between Low- and High-Density Amorphous Ice... 

II. PRESSURE-INDUCED AMORPHIZATION OF HEXAGONAL ICE HIGH-DENSITY AMORPHOUS ICE (HDA)... 

IV. APPARENT FIRST-ORDER TRANSITION BETWEEN LOW-AND HIGH-DENSITY AMORPHOUS ICE... 

R. J. Nelmes, J. S. Loveday, T. SUassle, C. L. Bull, M. Guthrie, G. Hamel, andS. Klotz, Atmealed high-density amorphous ice under presstue, Nat. Phys. 2. 414-418 (2006). 

As described below, the discovery of the high density amorphous ice (HDA) at low-temperature and high-pressure conditions was the beginning of a novel and promising idea about the liquid state in NML. 

Mishima, The glass to liquid transition of the emulsified high-density amorphous ice made by pressure-induced amorphization. J. Chem. Phys. 121, 3161-3164 (2004). 

T. Loerting, W. Schustereder, K. Winkel, C. G. Salzmann, I. Kohl, E. Mayer, Amorphous ice Stepwise formation of very-high-density amorphous ice from low-density amorphous ice at 125 K, Phys. Rev. Lett. 96 (2006) 025702. 

There exist different types of ice (see also Fig. 1.12). The ice we know from everyday live (also snow) has a hexagonal structure. At higher temperatures and pressures ice can also form a cubic structure 4). Other forms of ice are called II, III, V, VI, VII, VIII, IX and X. The difference between these forms is their crystalline structure. One also speaks of low-density amorphous ice (LDA), high-density amorphous ice (HDA), very high-density amorphous ice (VHDA) and hyperquenched glassy water (HGW). 

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