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SF

SF: Stacking Fault
Definition:Stacking faults, planar lattice defects
Explanation:SFs are planar lattice defects. These defects can be described by moving or inserting one layer of closed packed planes out or into the ideal perfect lattice. Two types stacking faults, intrinsic and extrinsic ones can be distinguished in face-centered cubic (→fcc) lattices. The ideal stacking sequence of the closed planes is ABCABCA in the fcc lattice (left image in Fig. 1) and ABABABA in the hexagonal closed-packed (HCP) structure, respectively. When a A layer is removed in some local region of the fcc lattice, a sequence of A[BC|BC]A can be observed. Here, a local HCP stacking sequence, [BCBC], can be distinguished, which is called as an intrinsic stacking fault (middle image in Fig. 1). In contrast, an extrinsic SF is formed by inserting one atomic layer of close packed planes. As shown in the right image in Fig 1., a layer B is added between A and C, resulting in an AB[C|B|ABC] sequence. The interrupted region poses a mirror lattice of the fcc stacking, [CBABC]. The extrinsic SF is also called as a double stacking fault [1].
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Diagram:

Fig. 1. Schematic representation of the intrinsic and extrinsic stacking faults [2].
SFB-Link:SF causes stacking fault energy (→SFE) which has an influence on the deformation mechanisms.
References:[1] J.Weertman, J.R.Weertman. Elementary dislocation theory. Macmillan, New York, 1964.
[2] J.Wang, S.Narayanan, J.Huang et al. Atomic-scale dynamic process of deformation-induced stacking fault tetrahedra in gold nanocrystals[J]. Nature communications, 2013, 4: 1-8.