Figure 6.

(A) Stack of MgO (100) planes with a vertical a_o/2[100] screw dislocation in the center, viewed at right angle. The screw dislocation is decorated by one [O₂C—C—C—CO₂] unit in the energetically favorable trans configuration with the medium size light gray spheres representing O⁻. (B) Oblique view of an edge dislocation in MgO with one row Mg²⁺ removed and two rows of O²⁻ changed to O⁻ (lighter gray spheres). (C) Same edge dislocation with C₄ units segregated into its core. Because of mismatch with the surrounding MgO matrix, the [O₂C—C—C—CO₂] units would have to adopt the energetically less favorable cis configuration.