Charged dislocations in lithium fluoride

The application of strong electrostatic fields to bent LiF crystals producod small motions (0·1 to 6 Å) of the bends which were analysed in terms of the motion of charged dislocations. The charge on the dislocation core was positive and of the order of 10−4 to 10−3 e.s.u./cm, and it presumably arose from the inequality of the free energies of formation of positive ion and negative ion vacancies. Estimates of the electrostatic contribution to the critical shear strength based on these values of charge substantiate the suggestion by Eshelby, Newey, Platt, and Lidiard that much of this strongth may be electrostatic in origin.