Solids high-density amorphous

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 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 first MD study of pressure-induced solid state amorphization was undertaken by Tse and Klein (1987). They showed that at 80 K ice Ih undergoes a transition to a high density amorphous form at around 13 kbar. 

The modulus of PE resins increases with increasing solid density. Thus, a HDPE resin has a higher modulus than an LDPE resin, as shown by the data in Table 2.3. In general, resins with low solid densities feel soft to the touch while resins with high densities feel hard. The and Tg for selected semicrystalline and amorphous materials are given in Table 2.3. 

These will act as Lewis acids. Hie catalytic sites occur at high density and are uniform in their activity (as opposed to amorphous solids because of the microcry.slalline nature of the zeolites. 

There are different criterion of how to classify solid-solid interfaces. One is the sharpness of the boundary. It could be abrupt on an atomic scale as, for example, in III-IV semiconductor heterostructures prepared by molecular beam epitaxy. In contrast, interdiffusion can create broad transitions. Surface reactions can lead to the formation of a thin layer of a new compound. The interfacial structure and composition will therefore depend on temperature, diffusion coefficient, miscibility, and reactivity of the components. Another criterion is the crystallinity of the interface. The interface may be crystalline-crystalline, crystalline-amorphous, or completely amorphous. Even when both solids are crystalline, the interface may be disturbed and exhibit a high density of defects. 

Otherwise, it is called amorphous. Solids have a high density and are almost incompressible because the molecules are close together. Diffusion occurs extremely slowly because the molecules almost never alter their position. 

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. 

B. Piriou and D. Alain, Density states and structural form related structural properties of amorphous solids. High Temp. High Press. Res. 11, pp. 407-414 (1979). 

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