Structures and energies of Σ3 asymmetric tilt grain boundaries in silicon

We optimize 23 silicon Σ3 asymmetric tilt grain boundaries (ATGBs) using Stillinger Weber (SW), Tersoff and the optimized Modified Embedded Atom Method (MEAM) potentials. It is demonstrated that conventional GB optimization via rigid body translations in combination with atom deletions is totally incapable of driving an as-constructed flat Si grain boundary (GB) to its equilibrated state since it may inevitably cause lattice distortions in GB. But it can be easily achieved by initially introducing some pre-designed steps into as-constructed flat GB model. These steps are composed of coherent twin boundary (CTB) and symmetric incoherent twin boundary (SITB) facets. By doing so, energies of all 23 ATGBs are greatly reduced. Meanwhile, some ATGBs may have degenerate states with different structures but same energies. This work not only facilitates the structural characterization of Si Σ3 ATGBs, but may provide new insights into microstructure design in polycrystalline silicon. Graphic Abstract