Defect clusters in wustite ${\mathrm{Fe}}_{1\mathrm{-}\mathrm{x}}$O

The electronic structure and stabilization energy of isolated defects and defect clusters in wustite ${\mathrm{Fe}}_{1\mathrm{-}\mathrm{x}}$O is studied by the first-principles local-density theory. The embedded-cluster model is used to obtain linear combination of atomic orbitals expansions of one-electron properties in the discrete-variational scheme. The stability of the 4:1 interstitial cluster relative to simple defects is verified, and the tendency of 4:1 clusters to aggregate is explored. Open edge- and vertex-shared aggregates which permit the close approach of charge-compensating ${\mathrm{Fe}}^{3+}$ ions are found to be energetically favored.