Strut-like bonds

The skeleton structure consists of strut-like bonds and vertices, with the struts connecting two kinds of vertices. The two vertices are replicas of the former octahedral and tetrahedral voids of the opal structure (Figure 3.8). These struts and vertices form a CaF2 lattice, in which the... 

The skeleton structure consists of strut-like bonds and vertices, with the struts connecting two kinds of vertices (Figure 6.3). The two vertices are replicas of the former octahedral and tetrahedral voids of the opal structure. These struts and vertices form a Cap2 lattice, in which the 8-coordinated square prism calcium (former octahedral voids of the opal) vertex is larger than the tetrahedral fluorine (former tetrahedral voids of the opal) vertex. The views toward the (111), (100), and (110) planes of the skeleton structure present the lozenge, hexagonal, and square arrangements, respectively. 

Most ceramics are intrinsically hard ionic or covalent bonds present an enormous lattice resistance to the motion of a dislocation. Take the covalent bond first. The covalent bond is localised the electrons which form the bond are concentrated in the region between the bonded atoms they behave like little elastic struts joining the atoms (Eig. 17.1b). When a dislocation moves through the structure it must break and reform... 

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