A simple method is given for obtaining root-mean-square electron-cloud radii y r.m.s. from diamagnetism. Comparison of these with structural radii r shows that for ionic and van der Waals bonds, r is about twice y r.m.s. ; for localised covalent bonds they are about equal. Comparison with theory shows that electron-cloud radii are about the same for localised-bond atoms, or for ions in crystals, as for the free particles with a notable exception in the hydride anion.

The widening world of magnetism

Structural radii, electron-cloud radii, ionic radii and solvation

What are (topological1) defects in matter ? Mathematically, they can be defined as singularities of a function Φ(x) associating a quantity, number, vector, etc., Φ∈M to any point x inside the material. Φ(x) represents the configuration of matter in the material. It is better to speak of topological entanglement instead of singularity, since we will encounter defects which are not singular. The aim of a general theory of defects is to associate topological entanglements to the set M of microscopic states of matter, and to classify them.

The widening world of magnetism

Citations

Structural radii, electron-cloud radii, ionic radii and solvation

Defects in quasicrystals, in systems with deterministic disorder and in amorphous materials