Figure 4.17. Plot similar to Figures 4.15 and 4.16 for Ag21. Contour lines are 0.1eV apart. The 3 additional electrons added to the 18 electrons of the closed shell introduce one unique local minimum with three unequal axes. Seen here are its six permutations. The global minimum is not spherical but is near (0,0) on this scale. For comparison, the IP's (not the total energies) are 4.21eV at the global minima near the center and 4.76eV at the six symmetrically equivalent local minima. This is a familiar pattern observed in the "shell+1" electron clusters.