Abstract
The microscopic structure of a silicon vacancy is studied theoreticallyusing first-principles supercell calculations. Both the standard Kohn–Shamlocal-density approximation (LDA) scheme and the generalized Kohn–Shamscreened-exchange local-density approximation (sX-LDA) scheme areused. The latter approximation is expected to improve the description ofelectronic levels in the gap region substantially, while providing accurate totalenergies and bond lengths.The present LDA calculations are in line withthe earlier corresponding calculations of the silicon vacancy, predictingan inward relaxation of the nearest neighbours of the vacant site. TheLDA calculations also predict the Jahn–Teller distortions and negativeeffective-Ueffects for charged vacancies, qualitatively in agreement with theexperimental results and the Watkins model. In contrast to LDA results, thepresent sX-LDA calculations predict an outward relaxation and sp2type hybridization for the ions surrounding the vacancy. This somewhat surprisingresult is explained by the removal of the systematic overbinding associated withLDA.
Published Version
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