Crystal cleavage method

FIGURE 1.19 Schematic illustration of Obreimow s single-crystal cleavage method. 

Two preferred methods for preparing clean surfaces consist of generating the surfaces under high vacuum at the beginning. Using remote control manipulators to crush a sample under vacuum exposes fresh surface to an environment in which adsorption equilibrium is very slow. This technique produces a heterogeneous array of crystal faces, however. Far more suitable for the specific and localized examination that diffraction methods offer is crystal cleavage... 

Fig. 1-22. A schematic representation of Fig. 1-23. Determination of surface the zero-creep method used to tension by single crystal cleavage...

In case of brittle solid materials, especially single crystals with clearly defined layer structure (e.g. mica), it is possible to use the cleavage method developed by Obreimow [44], In this method the crystal is split along the cleavage plane (Fig. 1-23), and the force that has to be applied to cause further development of the crack, Fc, is measured. 

Analytical Methods. Fluorite is readily identified by its crystal shape, usually simple cubes or interpenetrating twins, by its prominent octahedral cleavage, its relative softness, and the production of hydrogen fluoride when treated with sulfuric acid, evidenced by etching of glass. The presence of fluorite in ore specimens, or when associated with other fluorine-containing minerals, may be deterrnined by x-ray diffraction. 

Single crystals of zinc were broken106 by two cleavage and one tensile method. The 7 was about 100,400, and 575 erg/cm2, respectively, for these three arrangements. Also this wide spread of results is easier to reconcile with the new than with the Griffith theory. 

Compounds 53-55, 58, 59, 61, and 63-70 were prepared analogously to the syntheses of 56 and 57 according to Schemes 11 and 12, methods a (cleavage of three Si-O bonds). All reactions were carried out in acetonitrile at room temperature and the products isolated in high yields as crystalline solids. Compound 56 was obtained as the crystalline acetonitrile solvate 56 2CH3CN. Compounds 54,56,63,68, and 69 were isolated, after crystalli-... 

Although when examined using optical or even electron microscopy, crystal surfaces appear smooth, this is rarely the case. Techniques such as AFM and STM and optical interference methods (see Chap. 7) show that both growth and cleavage surfaces consist of terraces separated by steps which can be as little as one atomic layer... 

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