Lattice determinations by X-rays showed that the parameter of these small crystals was smaller than that of large crystals. in diameter were prepared in vacuo by Nicolson 26). NMR properties, 33 213, 274 in NMR studies of zeolites, 33 254-264 in sheet silicate studies, 33 342-345 - magnesium oxide catalyst, lattice parameter, 35 75. Magnesium oxide is an ionic solid that crystallizes in the sodium chloride type lattice. They found that maximum enhancement of potential occurred in a pore of width 4-4 A, where its numerical value was 3-2kcalmol, as compared with 1-12, 1-0 and 1-07 kcal mol for positions over a cation, an anion and the centre of a lattice ceil, respectively, on a freely exposed (100) surface of magnesium oxide. Anderson and Horlock, for example, used the Kirkwood-Miiller formulation in their calculations for argon adsorbed in slit-shaped pores of active magnesium oxide. Ĭalculations of the interaction energy in very fine pores are based on one or other of the standard expressions for the pair-wise interaction between atoms, already dealt with in Chapter 1. Surface stresses may produce wrinkling in harder materials.
An indirect estimate of surface tension may be obtained from the change in lattice parameters of small crystals such as magnesium oxide and sodium chloride owing to surface tensional compression however, these may represent nonequilibrium surface stress rather than surface tension.
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