Continuum dislocation/generalized-disclination modelling of a MgO {3 1 0}/[0 0 1] tilt boundary is proposed by using an atomistic-to-continuum crossover method. Using the relaxed and un-relaxed atomic positions obtained from first-principles simulations, calculation of the displacement, distortion (strain and rotation), curvature and second-order distortion fields is performed in the boundary area. The dislocation and disclination density fields are used to smoothly describe the discontinuities in the displacement and rotation fields across the boundary. In addition, a generalized-disclination density tensor field is introduced to reflect shear and stretch discontinuities across the boundary. This continuous model provides new mechanical insights into the structure of MgO grain boundary, as well as a basis for coarse-grained representations of the polycrystalline structure.

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