Implementation of Kunz-Klein localization in icecap and an application to the problem of off-center isovalent substitutional impurities in alkali halides

Theoretical models of off-center isovalent substitutional impurities in alkali halides are examined. Calculations have been performed on r,j+ in KCI, a representative system known experimentally to exhibit off-center behavior. The potential seen by the Li+ ion in the lattice has been calculated within the shell model using the computer program HADES and by means of an Unrestricted Hartree-Fock (UHF) cluster embedded in a shell model lattice using the computer program ICECAP. For the case using HADES, off-center behavior was predicted, and the resulting potential was used to predict the tunnelling splitting of the system and the Grueneisen parameter. The tunnelling splitting was calculated to be 1.19 meV for 7Li+ and 1.26 meV for 6Li+, compared to experimental results of 0.10 meV and 0.14 meV, respectively. The Grueneisen parameters were found to be 60 for 1Li+ and 66 for 6Li+, compared to experimental results of 150 for both isotopes. For the cases using ICECAP and UHF, off-center behavior was predicted, but the quantitative agreement with experimental barrier heights was not as good as that for HADES.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Keegstra, Phillip Brooks

Contributors dc:contributor

• Kunz, A.B.

• Kunz-Klein localization
• ICECAP
• Unrestricted Hartree-Fock (UHF)
• off-center isovalent substitutional impurities
• alkali halides

Statement dc:rights

• 1986 Phillip Brooks Keegstra

Language dc:language

en

Identifier

978710

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/25253