FIG. 3. A schematic of the relationship between super-cell and sub-cell (shaded) superimposed upon a PbO sheet. Solid circles are Pb sites that lie above and below the sheet of oxygen atoms (open circles). Asisite has a 26-cation-site motif [13 Pb(1) + 13 Pb(2)] within the sheet and there are two Si atoms (not shown explicitly) per super-sheet. The super-sheet repeat is 14.06 Å.