Effect of the axial ratio on planar fault energies in L10-type superlattice structures

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Abstract
A method of obtaining the planar fault energies in an L10-type superlattice structure is given as a function of the axial ratio R. Using this method, the anti-phase boundary (APB), stacking fault (SF) and complex stacking fault (CSF) energies are calculated for values of R ranging from 0.65 to 1.5. The increase and decrease in R from the minimum points near unity results in increases in these energies. For values of R, near unity, the APB energies increase in the following order: (1, 0, 0), (1, 1, 0), (1, 0, 1), (1, 1, 1) and (0, 0, 1). The APB energies on the (1, 0, 0) and (1, 1, 1) planes are reversed when R is larger than 14. The symmetry of a lattice structure after translation to form a SF and a CSF is considered. The translation vector b1 =⅙ or⅙ does not form a symmetrical SF or CSF structure if R is not equal to unity. Therefore the SF or CSF formed by b 1 might be unstable. Translation vectors for planar faults that are symmetrical in the L10 structure when R is not equal to unity are obtained. Such planar faults would be stable. The exchanges of the distances of the nearest-neighbour atom pairs for the second-nearest-neighbour ones, and of the second ones for the third ones occur at values of R of ∼0·7 and ∼ 1·2, respectively.