This image shows Ru 1? x Ir x Se 2 crystal structure considerations. Main panel shows 300 K experimental x-ray diffraction patterns (cross symbols) and refined structural model Pa-3 (solid red line), with difference curve (green solid line) offset for clarity for x = 0. Vertical ticks mark reflections. Data and model profiles for samples with x = 0.1 and 0.2 nominal composition are included and offset for clarity. Top left: evolution of lattice parameter with refined Ir content, solid line is guide for the eyes. Top right: pyrite-type crystal structure as seen along (111) direction, and distorted RuSe 6 corner shared octahedra representing basic building blocks of the structure.