Size effects, crystal

Elimination of Instrumental Broadening and Crystal Size Effect. Fourier transform of Eq. (8.13) turns the convolutions into multiplications (Sect. 2.7.8)... 

Thus, the interaction between structural entities of molecular and ionic crystals does not lead to appreciable delocalization of electrons strongly bonded to these entities. Therefore, the electronic structure of molecular and ionic crystals is practically not influenced by the size of such crystals. Size effects arise only in M/SC crystals with covalent (or at least partly covalent) bonds and depend on a relationship between the crystal size a and the length of delocalization (or, otherwise, electronic correlation) for valent electrons in a lattice. 

Groocock [16] made an experimental and theoretical study of the thermal explosion of lead azide but found no crystal size effect. However, he used batches of l0,000 crystals in vacuum so it was a different experiment from that of Bowden and Singh. The critical temperature for a batch of crystals will be reached when any one crystal reaches critical conditions, and this will be influenced by the heat transfer from neighboring crystals. Unfortunately, neither Bowden and Singh nor Groocock specify their vacuum conditions, although one can infer that Groocock s work was at lower pressures his analysis also assumes... 

For practical purposes, support interaction and crystal size effects mean that reduced catalysts will be oxidised when exposed to steam containing small amounts of H2 or to mixtures of steam and reducing... 

Polymer crystals are frequently small and imperfect, so that the diffraction spots are fuzzy, or they are arcs from an oriented polycrystalline texture. The degree of perfection of crystals of known structure can be determined from measurement of diffraction line widths and intensities. The analysis used for X-ray diffraction [25, 39, 40] can be transferred directly to electron diffraction. One can distinguish between crystal size effects and the effects of disorder within the crystals, but often a simple estimate of the mean crystal size, 0.9A/(angular breadth), is used. Any measure of disorder can only be an upper limit, unless careful precautions are taken to account for the effects of radiation damage. 

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