Equivalence of X-Ray Lattice Parameter and Density Changes in Neutron-Irradiated LiF

The lattice expansion in neutron-irradiated LiF was investigated in order to establish either Frenkel or Schottky defects as the cause of the expansion. For uniformly irradiated crystals, it was shown that x-ray lattice parameter and density changes are equivalent to within 6 percent. It follows that Schottky defects cannot account for more than 6 percent of the expansion and that Frenkel defects are predominant. The annealing of a nonuniformly irradiated crystal indicates a recovery process of order higher than one.