Very high density amorphous water

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). 

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]. 

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). 

Therefore, experiments are performed on immobilized liquids , or in other words on amorphous water (also called vitreous water or glassy water). Currently, three structurally distinct amorphous states of water are known low- (LDA) , high- (HDA) and very high- (VHDA) density amorphous ice We emphasize that HDA is not a well defined state but rather comprises a number of substates. It has been suggested to use the nomenclature uHDA ( unrelaxed HDA ) ", eHDA ( expanded HDA ) " and/or rHDA ( relaxed HDA ) to account for this. Even though no signs of micro-crystallinity have been found in neutron or X-ray diffraction studies, it is unclear whether... 

LDA forms by extremely quick cooling of liquid water ( hyperquenched glassy water , HGW), by depositing water vapour on very cold substrates ( amorphous solid water , ASW) or by heating high density forms of ice at ambient pressure ( LDA ). 

PMMA is the synthetic polymer of methyl methacrylate, which is widely known by a variety of trade names like Lucite, Oroglas, Perspex, Plexiglas, and so on. PMMA is a glassy polymer with an amorphous structure. It has a density of 1.19 g/cm and has very low water absorption. The refractive index ranges from 1.49 to 1.51 depending on the type. PMMA shows high... 

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