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Saddle‐Point Configuration of the F‐Centre in NaCl‐Type Alkali Halides
Author(s) -
Brown R. J.,
Vail J. M.
Publication year - 1970
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.19700400234
Subject(s) - saddle point , halide , alkali metal , ion , atomic physics , legendre polynomials , gaussian , lattice (music) , saddle , chemistry , physics , quantum mechanics , mathematics , geometry , inorganic chemistry , mathematical optimization , acoustics
Even and odd parity relaxed state energies for the saddle‐point F‐centre are evaluated, using gaussian‐localized, low‐order Legendre polynomial trial wave functions. A point‐ion model, with BSG ion‐size correction, is used, and lattice distortion (excluding ion polarization) is treated self‐consistently. A similar calculation is made for the ordinary F‐centre levels. Acceptable results are obtained for absorption, but not for emission. Agreement is obtained, within the rather large experimental error, with the activation energy for F‐centre step diffusion in KCl after correction of the ion‐ion repulsion at the saddle point. The results permit a critical assessment of the model.