Ion-size effects and the spatial extent of defects

• Published in: Radiation effects and defects in solids Vol. 155; no. 1-4; pp. 43 - 49
• Main Authors: Smith, D. Y., Inokuti, M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Reading Taylor & Francis Group 01.01.2001; Taylor and Francis
• Subjects: CATIONS; CHARGE DISTRIBUTION; Condensed matter: structure, mechanical and thermal properties; Defect size; Defects and impurities in crystals; microstructure; ELECTRONIC STRUCTURE; ENDOR; Exact sciences and technology; F CENTERS; F centres; IONS; Localization; MATERIALS SCIENCE; Orthogonalization; PAULI PRINCIPLE; Physics; Point defects (vacancies, interstitials, color centers, etc.) and defect clusters; SOLIDS; Structure of solids and liquids; crystallography; Sum rules; WAVE FUNCTIONS; Nearest neighbour; Inorganic compounds; Point defects; Pauli principle; F centers; Size effect; Theoretical study; Orthogonalized orbital; Alkali metal halides; Color centers; Localization; Ionic crystals
• ISSN: 1042-0150; 1029-4953
• DOI: 10.1080/10420150108214090

Analysis of the F-centre's optical absorption indicates that the radii of centres with large cation neighbours are greater than the radii of those with smaller neighbours. We resolve this apparent conflict with the Pauli exclusion principle by calculating the rms radii of point-ion model wave functions orthogonalized to the occupied core states of nearest-neighbour ions. Orthogonality to s-like ion-core states shifts defect charge toward neighbours' nuclei. This yields negligible change in rms size, but a large increase in hyperfine interaction, an effect established by ENDOR. Orthogonalization to p-like core states relocates charge lying between the F-centre and the ions to the outer sides of the ions expanding the defect charge distribution. The larger the neighbours, the greater is the expansion.