Equilibrium structures of elemental materials and binary compounds in black-phosphorene-type phase-I, (b) blue-phosphorene-type phase-II, (c) indium-iodide-type phase-III, and their ternary counterparts in (d) phase-I and (e) phase-II. All structure are shown in both top and side views. The different colors represent the V-group, or IV–VI, or III–VII elements without any specifications, except that the brown in (c) represents the III-group element, the dark purple in (d) and the light green in (e) represent the III- or IV-group element, and the grey in (d), (e) represents the VII-group element.