PROPRIÉTÉS GÉNÉRALES DES CENTRES COLORÉSTHEORETICAL STUDIES OF SOME ACTIVATION ENERGIES OF F- AND FΛ-CENTRES IN KClReport as inadecuate




PROPRIÉTÉS GÉNÉRALES DES CENTRES COLORÉSTHEORETICAL STUDIES OF SOME ACTIVATION ENERGIES OF F- AND FΛ-CENTRES IN KCl - Download this document for free, or read online. Document in PDF available to download.



Abstract : The activation energies for step-diffusion of the F-centre and reorientation of FANa and FALi-centres in KCl are analysed theoretically. For each defect in both ground and first excited states, the activation energy is expressed as a sum of contributions from a the excess electron-s kinetic energy, b its interaction with the lattice unpolarizable point ions with BSG ion-size correction, c the lattice energy of the defect, and d the net effect of harmonic lattice distortion, not included in a-c. The method of lattice statics is applied, with the electronic state and lattice distortion determined self-consistently, using the variational method. When the activation energies are compared with experiment, we find the F-centre results about 0.5 eV too high, but qualitatively correct, the FANa and FALi ground state results in good agreement, and the FALi, relaxed excited state RES result qualitatively correct. The excess electron-s kinetic energy is dominant in lowering the RES activation energy relative to that in the ground state, and the effect of small impurities Na+ and Li+ in lowering the activation energies in both states is about equally divided between lattice energy and Coulomb electron-lattice interaction.





Author: J. Vail R. Brown C. Ong

Source: https://hal.archives-ouvertes.fr/



DOWNLOAD PDF




Related documents