Relative Surface Tensions from Equilibrium Crystal Shapes

Relative Surface Tensions from Equilibrium Crystal Shapes 

We noted in Section VII-2B that, given the set of surface tension values for various crystal planes, the Wulff theorem allowed the construction of fhe equilibrium or minimum firee energy shape. This concept may be applied in reverse small crystals will gradually take on their equilibrium shape upon annealing near their melting point and likewise, small air pockets in a crystal will form equilibrium-shaped voids. The latter phenomenon offers the possible advantage that adventitious contamination of the solid-air interface is less likely. 

Nelson et al. [34] determined from void shapes that the ratio 7100/7110 was 1.2, 0.98 and 1.14 for copper at 600°C, aluminum at 550°C, and molybdenum at 2000°C, respectively, and 1.03 for 7100/7111 for aluminum at 450°C. Metal tips in field emission studies (see Section VIII-2C) tend to take on an equilibrium faceting into shapes agreeing fairly well with calculations [133]. 

Sundquist [35], studying small crystals of metals, noted a great tendency for rather rounded shapes and concluded that for such metals as silver, gold, copper, and iron there was not more than about 15% variation in surface tension between different crystal 

Dependence of Other Physical Properties on Surface Energy Changes at a Solid Interface 

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C. Relative Surface Tensions from Equilibrium Crystal Shapes... 

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