RECHERCHES THÉORIQUES SUR LA DIFFUSION DES LACUNES DANS LES CRISTAUX IONIQUES DU TYPE CHLORURE DE SODIUM

Résumé
On a déterminé la distribution de l'énergie potentielle régissant la migration d'une lacune cationique dans quelques halogénures alcalins. On a pu tracer, en première approximation, les barrières de potentiel. Le complexe de diffusion correspond à un réarrangement complet des ions autour de l'ion mobile.

Abstract
The determination of the potential surfaces governing the diffusion of a cationic vacancy in alkaline halides implies the following conclusions : 1) The neighbours of the vacancy are displaced by less than ten percent except in the case of lithium where moreover it is necessary to take into account some delocalisation by quantic penetration. 2) The reaction path is linear ; the potential barrier is of the order of magnitude of 1 eV except in the case of lithium halides where it is less than 0.1 eV. 3) Diffusion complexe is surrounded by a small depression of the potential ; at this point a completely new structuration of ions, corresponding approximatively to the rule of ionic radius, occurs.