3. The crystal structure of a pure face-centered-cubic metal (such as copper) is shown on the following page. In part (i.), all the atoms that are in a single unit cell are shown. In (ii.), the atoms have been "cut off so that only what is inside a single unit cell is shown. In (ii.), the front face of one unit cell is shown. The atomic radius of copper is 0.125 nm. 2r 3 12ao (i.) (ii.) (111) (a.) Calculate the diameter of an octahedral site (denoted D in the figure). The hard-sphere model applies here. (b.) The radius of an oxygen atom is taken as 0.074 nm. Does it fit in the interstitial hole? If not, what is percent oversize or undersize? Note: I recommend the following: % under or oversize = actual size of atom -- size of hole X 100 size of hole (c.) Next, consider replacing or substituting an oxygen atom for a copper atom. Obviously the oxygen atom is too small, but by how much (percent undersized)? Again, I suggest using the equation above. (d. If the percent undersize or oversize provide key predictive outcomes, then which site is favored for oxygen in otherwise pure copper