Principle Bernhardi

From here we arrive at the Bernhardi principle (1809) The number and dimensions of the faces are not characteristic for a crystal every crystal has its own habit. Only the directions and orientations are important, in other words, the... 

Fig. 1.4. The Bernhardi principle three polyhedra with the same angles of 60° and 90° between the normals to the faces...

What is the relation between the space group which describes the symmetry of a crystal structure at the atomic level and the point group which describes the symmetry of the corresponding macroscopic crystal By analogy with the Bernhardi principle (Section 1.3.1), a crystal is characterized by its properties in different directions, for example rate of growth, thermal and electrical conductivity, elasticity and piezoelectricity. Let us consider the periodic structure shown in Fig. 2.12. Clearly, the macroscopic properties in the directions of the two large... 

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See also in sourсe #XX -- [ ]

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