Embedded-cluster quantum-chemistry calculations were made of hyperfine interactions of the F center. The values of the isotropic hyperfine interaction exhibited good general agreement with experiment. It was shown that careful treatment of the lattice environment, local lattice distortion and spin polarization was important to this agreement.

Hyperfine Interactions and Lattice Distortion of the F Center in KCl, NaCl and LiCl Crystals. A.A.Leitão, R.B.Capaz, N.V.Vugman, C.E.Bielschowsky: Journal of Molecular Structure - THEOCHEM, 2002, 580[1-3], 65-73