Fig. 3: Atomic displacements during etching.

a Displacements of atoms found in both structures I and II, structures II and III, and structures III and IV. Red spheres are atoms in the preceding map, and blue spheres are atoms in the following map. Semi-transparent spheres are defined to include the atoms in the preceding and following maps. The surfaces of those spheres are color-coded by atomic displacement and are indicated by the color scale. b–d Distributions of atomic displacements between atoms found in structures I and II (b), structures II and III (c), and structures III and IV (d). e, f Atomic structures of representative (¯1¯11) surfaces in structures III and IV, viewed from the directions normal (e) and parallel (f) to the (¯1¯11) surface. Cyan circles show the locations of surface atoms in the top layer of structure III. Blue circles show the locations of surface atoms in structure IV which are displaced relative to structure III. White circles show removed atoms. g Displacements of atoms between structures III and IV depending on coordination numbers obtained from structure III. h Mean Pt–Pt distances of individual surface Pt atoms in structures III (triangles) and IV (diamonds). Curves are Gaussian fits. Scale bars, 5 Å. Source data are provided as a Source Data file.