Defect properties of BaFBr, BaFCl, and SrFCl were calculated using the atomistic simulation technique. Two-body potentials were developed starting from potentials in related crystals or calculated by the electron-gas method and then fit to minimize strain in the equilibrium structure. Agreement of calculated elastic, dielectric, and cohesive properties with available experimental and theoretical data was reasonable. Generally, Frenkel energies for the larger-size halogen ion were less than for the fluorine ion and less than the Schottky energy for the metal, fluoride, and other halide ions set. A Schottky energy for vacancies of the metal ion and two of the larger-size halide ions was small. Energies of formation of ${V}_{k}$ and H centers were computed with the aid of thermodynamic cycles. The most stable ${V}_{k}$ center forms on the halide ion site where the Madelung potential is most favorable for holes. H centers occupy off-center sites in these low-symmetry materials. Stable geometries are discussed.