SHOCK-WAVE SYNTHESIS OF HIGH-DENSITY MODIFICATIONS OF ZINC OXIDE (REVIEW)

According to the geometric model an ionic crystal consists of ionic spheres with a definite radius. Each coordination polyhedron (icosahedron, cube, octahedron, tetrahedron, regular triangle) has a critical (minimum) ratio Rc Ra of the radii of the cation and anion with which it can be formed (anions touch cations as well as one another). The probability of any particular coordination of the cations can be estimated by means of the Magnus – Goldschmidt criterion: a coordination polyhedron forms in a structure if the ratio R c R a is greater than a critical value. The ratio Rc Ra = 1 for an icosahedron, 0.731 for a cube, 0.414 for an octahedron, 0.225 for a tetrahedron, and 0.155 for a triangle.