Atomistic calculation of the core structure and Peierls energy of an (a/2) [110] edge dislocation in MgO

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Abstract
The core configuration and energies of the two symmetric configurations of an (a/2) [110] edge dislocation in a model MgO crystal were calculated atomistically using a point‐ion or shell model with a rigid boundary region. Two short‐range potentials and one set of shell‐model parameters used in the present calculation were developed by Catlow, Faux, and Norgett who employed them to calculate Schottky defect energies and volumes of formation in MgO. The two symmetric dislocation configurations investigated turned out to have unequal energies, but which dislocation configuration had the higher energy depended on the particular version of the short‐range potential. The shell model yielded dislocation strain energies which were approximately 0.24 eV/repeat distance lower than the corresponding strain energies for the point‐ion model. The atomistically calculated energy factors derived from a strain‐energy–vs–lnr plot were, in all cases, larger than the corresponding values derived from anisotropic elasticity theory. The Peierls energy barrier separating two equal‐energy dislocation configurations was calculated using a linear interpolation technique. These calculations showed that the higher‐energy symmetric dislocation configuration was situated either in a small local minimum or on top of a very flat‐topped ’’Peierls hill’’. The maximum value of the Peierls barrier varied between 0.012 and 0.042 eV/repeat distance, depending on the method and the potential used to calculate it. The Peierls stress derived from the Peierls energy calculations ranged between 162 and 383 MPa.