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

TL;DR

This study investigates the structure and energy variations of silicon (001) small angle mixed grain boundaries as functions of tilt, twist, and rotation characters, providing a comprehensive model and insights into their structural transitions and formation mechanisms.

Contribution

It introduces a revised Read-Shockley model for describing grain boundary energies in three-dimensional character space and analyzes structural transitions and formation mechanisms of SAMGBs.

Findings

Revised Read-Shockley relationship accurately describes energy variations.

Identification of structural transitions from dislocation to amorphous states.

Mechanistic insights into dislocation glide and reactions in SAMGB formation.

Abstract

Understanding how dislocation structures vary with grain boundary (GB) characters enables accurate controls of interfacial nano-patterns. In this atomistic study, we report the structure-property correlations of Si (001) small angle mixed grain boundaries (SAMGBs) under three macroscopic GB characters (tilt character, twist character, and an implicit rotation character between them). Firstly, the SAMGB energies are computed as a function of tilt angle, twist angle and rotation angle, based on which a revised Read-Shockley relationship capable of precisely describing the energy variations span the three-dimensional GB character space is fitted. Secondly, GB structural transitions from dislocation to amorphous structures are given as a function of tilt angle, twist angle and dislocation core radii. The proportion, topology and structural signatures of different SAMGB types defined from the ratio between the tilt and twist angles are also presented. Thirdly, by extracting the transformation of metastable SAMGB phases, the formation mechanisms of SAMGB structures are characterized as 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.