Arrangement of polyhedral units for [0001]-symmetrical tilt grain boundaries in zinc oxide

Atomistic structures of 〈0001〉 tilt grain boundaries in a textured Mg thin film

“…The higher dislocation density of type-2 GBs with respect to their type-1 counterparts leads to their higher energy formation energy, and hence rarer occurrences. We further note that similar atomic configurations of type-1 and type-2 GBs have been characterized for ZnO 9 , so that our finding with regard to the energetics and structure of type-1 and type-2 <0001> symmetric tilt GBs should be applicable to HCP crystals in general. Simulation reports on <0001> symmetric tilt GBs in HCP Ti have demonstrated a higher energy of type-2 GBs.…”

“…Such an arrangement of dislocation arrays has been reported for type-2 GBs in ZnO, another crystal with a HCP structure. 9 Like for type-1 GBs, we can apply Frank's formula to calculate the dislocation spacing 2D between arrays of b 1 + b 2 dislocations (for Mg, ), replacing θ > 30° to the small angles 60° − θ in eqn (4),For type-2 Σ 37 〈0001〉 symmetric tilt GB ( θ = 50.57°), the dislocation spacing is D = 1.69 nm. In comparison, the dislocation spacing for its type-1 counterpart ( θ = 9.43°), D = 1.95 nm, is wider (less dense) by a factor of .…”

“…6,7 In comparison, there are fewer studies on GBs in another common crystal structure, hexagonal close-packed (HCP), including Mg, Ti, 8 , and ZnO. 9 Mg is among the metallic elements with the lowest density (1.74 g cm −3 ) and Mg-based alloys have found increasing applications in lightweight structural systems, shielding for electronics, implants, and energy storage. 10 Due to the HCP crystal structure, Mg has a limited number of slip and twin systems for plastic deformation.…”

“…6,7 In comparison, there are fewer studies on GBs in another common crystal structure, hexagonal close-packed (HCP), including Mg, Ti, 8 and ZnO. 9…”

“…Complete list of <0001> symmetric tilt GBs with Σ < 100. Σ is introduced to consider both atoms in the HCP unit cell after rotation 9. …”