Formation mechanism of tetrahedral MgYNi4 phase

• MgYNi4 is obtained by melting method in resistance furnace.
• The 3D morphology of MgYNi4 single crystal is observed.
• Close-packed plane observed in HRTEM image agrees well with structure model.
• Formation mechanism of tetrahedral MgYNi4 is proposed.

A tetrahedral MgYNi4 phase is prepared by melting method, and then formation mechanism associated with three-dimensional (3D) morphology is proposed. The tetrahedral MgYNi4 crystal is enclosed by four closed-packed {111} planes, arising from the 4-fold rotoinversion symmetry of MgYNi4 structure. The secondary arms grow along <110> directions between four primary trunks. The {111} lamellas grow from secondary arms to face center and shape up a tetrahedral skeleton with hollows. As {111} lamellas grow, the skeleton can be filled up and the perfect tetrahedral MgYNi4 is formed.

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