Structures and energies of computed silicon (001) small angle mixed grain boundaries as a function of three macroscopic characters.

Small angle grain boundaries comprised of dislocation structures have unique impacts on the performances of crystalline materials. In this atomistic study, we report structure-property correlations of Si (001) small angle mixed grain boundaries (SAMGBs) across three macroscopic GB characters (tilt character, twist character, and an implicit rotation character between them). Firstly, for the computed SAMGB energies spanning the three-dimensional GB character space, a revised Read-Shockley relationship is proposed and fitted, which hints that the energy trends follow the Read-Shockley formalism from the insight of GB decomposition. GB structural transitions from dislocation to amorphous structures are also given as a function of dislocation core radii, allowing the estimation of small angle GB proportion. Then, the proportion, topology and structural signatures of different SAMGB types defined from the ratio between the tilt and twist angles are presented. By extracting the transformation of metastable SAMGB phases, the formation process of these (001) SAMGB structures is characterized as the energetically favorable dislocation glide and reaction, from which the dislocation density function is derived. The relevant results about SAMGB energies and structures are validated and supported by theoretical calculations and experimental observations, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]