Dislocation core structures in α quartz derived from a valence force potential

The minimum core energies of inequivalent perfect dislocations in α quartz with Burgers vector a1, a2 or c find line direction a2 or c are evaluated using a Keating-type valence force potential fitted to phonon dispersion curves. Dislocations that are dissociated or contain dangling bonds, valence alternation defects or non-stoichiometry arc not considered. The low values of the core energies for the lowest-energy structure of each dislocation type, generally in the range 2–5 eV, appear to justify the last three restrictions, with the possible exception of c screw dislocations which should have core energies not lower than 6 eV.