Atomic Arrangements in Glass

Zachariasen, W. H. (1932). The atomic arrangement in glass. Journal of the American Chemical Society, 54, 3841-51. 

Zachariasen, W.H. (1932) The atomic arrangement in glass, J. Am. Chem. Soc. 54, 3841. The random network model for glass structure has been the dominant factor in developing glass formulations for 70 years. This is the classic reference for that model. 

Figure 6.11. Atomic arrangement in glass fibers after the introduction of impurities.

Fig. la. Atomic structure ofa two-dimensional nano-structured material. For the sake of clarity, the atoms in the centers of the crystals are indicated in black. The ones in the boundary core regions are represented by open circles. Both types of atoms are assumed to be chemically identical b Atomic arrangement in a two-dimensional glass (hard sphere model), c Atomic structure of a two-dimensional nanostructured material consisting Of elastically distorted crystallites. The distortion results from the incorporation of large solute atoms. In the vicinity of the large solute atoms, the lattice planes are curved as indicated in the crystallite on the lower left side. This is not so if all atoms have the same size as indicated in Fig. la [13]... 

Figure 9-61. Zachariasen s [129] representation of the atomic arrangement in the crystal (a) and glass (b) of A203.

A crystal may be defined as a solid composed of atoms arranged in a pattern periodic in three dimensions. As such, crystals differ in a fundamental way from gases and liquids because the atomic arrangements in the latter do not possess the essential requirement of periodicity. Not all solids are crystalline, however some are amorphous, like glass, and do not have any regular interior arrangement of atoms. There is, in fact, no essential difference between an amorphous solid and a liquid, and the former is often referred to as an undercooled liquid. ... 

Understanding atomic bonding helps us understand the structures of crystals and glass. When we think of crystals, we think of atoms arranged in a perfect way. We traditionally think in terms of crystal defects, but we will also consider how these ideas apply to defects in glass. 

In a first approximation one may assume that the atomic arrangement in all amorphous alloys is similar and corresponds to a statistical distribution of atoms. In that case the values of can be taken to be the same in all alloys. The thermal stability of the glass, when expressed in terms of (or its upper limit T ), is therefore mainly determined by AE. In fact one would derive from eq. (14) that (or Tjj) in all alloys is proportional to AE, i.e. 

Fig. 1. Schematic two-dimensional illustration of the atomic arrangement in (a) crystal and (b) glass (Carter Norton, 2007)...

Fig. 9.10. Sulphur, glasses and polymers turn into viscous liquids at high temperature. The atoms in the liquid ore arranged in long polymerised chains. The liquids ore viscous because it is difficult to get these bulky chains to slide over one another. It is also hard to get the atoms to regroup themselves into crystals, and the kinetics of crystallisation are very slow. The liquid can easily be cooled past the nose of the C-curve to give a metastable supercooled liquid which can survive for long times at room temperature.

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