Figure 4

(a) Sketch of Bi atomic arrangement that satisfies 6a_Bi = 7a_Si. The Bi atoms form a \(2\sqrt 3 \times 2\sqrt 3\) (a_Bi) supercell indicated by a dashed hexagon. (b) Sketch of the misaligned atomic arrangement. The Bi atoms form a \(3 \times 3\) (a_Bi) supercell indicated by a dashed hexagon.