Amorphous atomic rearrangement

Weber, T. A., and Stillinger, F. H., Interactions, local order, and atomic rearrangement kinetics in amorphous nickel-phosphorus alloys. Phys. Rev. B 32,5402 (1985). 

To describe the thermodynamics and kinetics of clusters with due regard for the multiplicity of the structure states (SS) of these nuclei, it is necessary to introduce the SS sets. The mutual transformations of clusters by atom attach ment or detachment, or by atom rearrangements are possible. It means that the SS set may be ordered to form a space. Then, it is possible to consider the nucleation of noncrystalline nuclei (clusters) as a diffusion process in an extended space of cluster structure states (CSS), which is, in fact, the join of hierarchy of ultrametric subspaces. The kinetic criterion of glass transition can be formulated as a condition of the overwhelming transformation of a liquid into a noncrystalline amorphous solid. 

In a typical plasma jet, the reactants are heated to their melting temperatures, causing a fraction of the particles to vaporize and react with each other. The atomic and molecular product clusters are then quenched. This happens in a few milliseconds, which doesn t allow enough time for the atomic rearrangement required for the formation of crystalline structures, resulting in new amorphous and other metastable phases. 

Extended x-ray absorption fine stmcture measurements (EXAFS) have been performed to iavestigate the short-range stmcture of TbFe films (46). It is observed that there is an excess number of Fe—Fe and Tb—Tb pairs ia the plane of the amorphous film and an excess number of Tb—Fe pairs perpendicular to film. The iacrease of K with the substrate temperature for samples prepared by evaporation is explained by a rearrangement of local absorbed atom configurations duting the growth of the film (surface-iaduced textuting) (47). 

The surface groups S with the highest free energy should be most efficient in the processes of chemical modification. In this case, one can expect the formation of a great variety of modification products (SR groups). For the compounds with the directional chemical bonds between the neighboring atoms in the main crystalline and amorphous silica modifications, these are the products of bond rupture and/or its rearrangement. 

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