Radiusverhältnisses

Radiusverhältnisses, often translated as radius ratio, is a concept used in chemistry and materials science to describe the relative sizes of ions in an ionic compound or the ratio of radii in various geometric structures. It plays a crucial role in determining the coordination number and the stability of crystal lattices. In the context of ionic compounds, the radius ratio is calculated by dividing the radius of the smaller ion by the radius of the larger ion. This ratio provides insight into how the smaller ions can fit into the spaces, or interstices, created by the larger ions in a crystal structure.

Different radius ratio ranges correspond to specific coordination numbers. For instance, a radius ratio between approximately 0.225 and 0.414 often suggests a tetrahedral coordination, where four larger ions surround a central smaller ion. A ratio between 0.414 and 0.732 typically indicates an octahedral coordination, with six larger ions around a central smaller one. Ratios above 0.732 suggest cubic coordination. These geometrical constraints influence the packing efficiency and the overall stability of the ionic lattice. Understanding the radius ratio helps predict the structure and properties of ionic solids.