Very high-density amorphous

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. 

The possibility of the existence of a second liquid-liquid phase transition in water was discussed following the discovery [42] of an even higher density amorphous state, named very high density amorphous (VHDA). However, unlike the LDA-HDA transition, this has since been widely accepted to be a continuous change in the structure [74]. 

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). 

Using different deposition rates, even a highly compacted form of amorphous solid water of density > 1 g/cm3 could be obtained at deposition temperature T < 30 K, which transforms gradually in the temperature range 38-68 K to the lower density form of density 0.94 g/cm3 [139, 140]. This transition was proposed to be at the origin of crack-formation processes in comets [141]. We note, however, that the formation of this high-density amorph at very low temperatures has been doubted [142, 143]. Only photolysis at 20 K induces a transition to a high-density amorph [143]. 

Giovambattista N., Stanley H., Sciortino F. (2005) Relation between the High Density Phase and the Very-High Density Phase of Amorphous Solid Water, T /2j5. Rev. Lett. 94(10), 107803-107807. 

N. Giovambattista, H. E. Stanley, and F. Sciortino, Relation between the high density phase and the very-high density phase of amorphous solid water, Phys. Rev. Lett. 94, 107803/1-107803/4 (2005). 

The amorphous phase differs from the mesophase and the crystalline phase by a clearly lower value of density. The amorphous phase density depends on the internal orientation of the fiber. Us value is in the range 1.335-1.357 g/cm. In the case of a very high orientation, it can even reach the value 1.363 g/cm-. ... 

Stress-corrosion cracking based on active-path corrosion of amorphous alloys has so far only been found when alloys of very low corrosion resistance are corroded under very high applied stresses . However, when the corrosion resistance is sufficiently high, plastic deformation does not affect the passive current density or the pitting potential , and hence amorphous alloys are immune from stress-corrosion cracking. 

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