Crystal structure of the mirror symmetry 10H-type long-period stacking order phase in Mg–Y–Zn alloy

The crystal structure of the 10H-type long-period stacking order structure in Mg–Y–Zn alloy was investigated by first-principle calculations. The calculated results show that the accurate positions and distinctive arrangement of Zn and Y atoms in the most stable 10H-type LPSO phase exhibit mirror symmetry with respect to the atomic layer C6, which agrees well with the experimental observations. Theoretical calculations still indicate that the mirror symmetry 10H-type ABACBCBCAB phase is not distorted, the lattice distortion of other LPSO phases may originate from the asymmetry of Zn element in the chemical order and stacking order. The obtained electronic density of states (DOS) reveals the underlying mechanism for mirror symmetry of 10H-LPSO phase.

Research highlights▶ 10H phase has the unique mirror symmetry with ABACBCBCAB stacking sequence. ▶ The special mirror symmetry of stacking sequences would be related to the distinctive atomic configurations and novel mechanical properties. ▶ The present theoretical calculations first reveal the unique feature of arrangement and distribution of Y and Zn atoms in the mirror symmetry 10H-type LPSO phase. ▶ Furthermore, it is found that the most stable 10H-type phase with mirror symmetry has not structural distortion, implying that the lattice distortion in the LPSO phase is likely to originate from the asymmetry of the Zn element in the chemical order as well as stacking order. ▶ Interestingly, the distribution of Zn and Y in the novel structure still provide useful cue to the inter-transformation between various LPSO structures.