Silicate glasses short-range order

Figure 11. X-ray diffraction patterns and EXAFS radial structure functions of two poorly-ciystallized compounds. Both ferrihydrite and silicate glass look amorphous through XRD, but the former is as well short-range ordered as feroxyhite, whereas the latter is disordered even at the local scale. Ge02 is used as the EXAFS example instead of Si02 to better match the second-neighbor scattering factors for the Fe oxides.

$Figure 11. X-ray diffraction patterns and EXAFS radial structure functions of two poorly-ciystallized compounds. Both ferrihydrite and silicate glass look amorphous through XRD, but the former is as well short-range ordered as feroxyhite, whereas the latter is disordered even at the local scale. Ge02 is used as the EXAFS example instead of Si02 to better match the second-neighbor scattering factors for the Fe oxides.$

The density of amorphous materials is just a few per cent lower than that of crystals of the same composition the short-range order in both is expected to be comparable. An illustrative example of the occurrence of short-range order in an amorphous material is provided by silicate glasses. [Pg.243]

In addition to the large number of silicate crystals, the Si04 tetrahedra are the basis of many glasses in which the structure derives from that of the liquid state. These structures have short-range but not long-range order. [Pg.144]

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