Simulation of theVkcenter in LiF using Hartree-Fock clusters

The role of accurate solid-state modeling to describe charged defects in ionic crystals is assessed in several well-defined models using a well-characterized point defect: the $V_k$ center. This defect is considered as a ${\mathrm{F}}_2^{-}$ molecular ion in LiF and is simulated using Hartree-Fock molecular clusters consisting of the defect and/or its nearest-neighbor ${\mathrm{Li}}^{+}$ ions. We find that the stabilization energy of the defect is almost entirely controlled by the presence of the distorted lattice whereas the internuclear separation in the defect appears to be affected by the crystalline environment. The hyperfine constants for the defect and the neighboring nuclei are calculated and compared with experiment.