Fcenter in LiF: A quantum mechanicalab initioinvestigation of the hyperfine interaction between the unpaired electron at the vacancy and its first seven neighbors

The paramagnetic F center in LiF is investigated at a quantum mechanical level with the CRYSTAL98 periodic code by using a supercell scheme. The isotropic and anisotropic components of the hyperfine coupling tensor describing the interaction between the unpaired electron and the nuclear spins up to the seventh nearest neighbors of the defect are computed by using two different Hamiltonians (Hartree-Fock and local density approximation), and turn out to compare reasonably well with electron paramagnetic resonance and electron-nuclear double resonance data. A term of the hyperfine tensor, not yet available experimentally, is presented for future comparison. The defect wave function is analyzed in terms of the charge and spin density maps, band structure, and Mulliken population.