EFFECT OF THERMAL-NEUTRON IRRADIATION ON ELASTIC MODULI OF LIF

The three eleastic-constant changes, and the dilation, of LiF have been measured as a function of neutron flux. The elastic constants all decrease with flux, the change being linear for fluxes less than 1016 n/cm2. This is contrary to expectations based on considerations of Dienes and Nabarro, and consequently, it makes measurements of elastic constants less useful as a tool for distinguishing between interstitials and vacancies than had previously been expected. The ratio of the relative bulk modulus to the volume change is - 1.8, which is much smaller than some corresponding values previously reported for copper. A comparison of the experimental results with various available theories shows that a nonlinear elastic sphere-inhole calculation disagrees the least, the expectations from Zener's considerations come next, and the rest of the theoretical estimates differ in order of magnitude and even in sign from the experimental results. © 1969 The American Physical Society.