SFE extrinsic

SFE extrinsic: Stacking Fault Energy, extrinsic
Definition:Extrinsic stacking fault energy
Explanation:A stacking fault (→SF) is a one or two layer interruption in the stacking sequence of the crystal structure. These interruptions carry certain stacking fault energy (→SFE). SFs have the same two dimensional periodicity (on the xy plane) as the ideal structure. The irregularities introduced by the faults break the periodicity in the third dimensions (z direction) only. The extrinsic SF is formed by inserting an atomic layer into the nine atomic layers stacked with the normal order ABCABCABC. A ten atomic layers repeat unit with the order ABCABAVABC is obtained [1]. The extrinsic SFs appear once in each ten layers periodically. Such extrinsic SFs cause extrinsic SFE. Fig. 1 shows the comparison between perfect fcc (111) surface structure and extrinsic SF [2]. The energy stored in extrinsic SF is extrinsic SFE.
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Fig. 1. FCC (111) surface perfect structures (left) and with extrinsic stacking fault (right) [2]
SFB-Link:SF causes SFE which has an influence on the deformation mechanisms.
References:[1] Q.Jin, P.Wang, D.Ding. ASW first principles calculation of the intrinsic and extrinsic stacking fault energies in aluminium[J]. Physics Letters A, 1993, 174: 437-440.
[2] M.Muzyk, Z.Pakiela, K.J.Kurzydlowski. Ab initio calculations of the generalized stacking fault energy in aluminium alloys[J]. Scripta materialia, 2011, 64, 916-918.