Question

3. A biology student has just come back from a spelunking trip and gives you a crystal he found. He wants to find out whether this is gold or just Fool’s gold. You suggest using XRD to distinguish the two materials. You find out that Fool’s gold is FeS2 and has a cubic structure. The peaks with the highest d spacings are 2.355 à and 3.128 à for Au and FeS2, respectively, and both peaks have identical (hkl) indices. a) Calculate the lattice parameter for Fool’s gold. b) How much lighter will the nugget be if it is Fool’s gold, compared to gold (assume that Fool’s gold has the same # of molecules/unit cell as gold has atoms/unit cell)? c) Sketch the (200) plane in a unit cell of Au and give the number of atoms in that plane. d) Sketch and label a direction within the Au unit cell that has the maximum linear density (i.e., the maximum number of atoms/unit length of line).

3. A biology student has just come back from a spelunking trip and gives you a crystal he found. He wants to find out whether this is gold or just Fool's gold. You suggest using XRD to distinguish the two materials. You find out that Fool's gold is FeS2 and has a cubic structure. The peaks with the highest d spacings are 2.355 Ã and 3.128 Ã for Au and FeS2, respectively, and both peaks have identical (hkl) indices. a) Calculate the lattice parameter for Fool's gold. b) How much lighter will the nugget be if it is Fool's gold, compared to gold (assume that Fool's gold has the same # of molecules/unit cell as gold has atoms/unit cell)? c) Sketch the (200) plane in a unit cell of Au and give the number of atoms in that plane d) Sketch and label a direction within the Au unit cell that has the maximum linear density (i.e., the maximum number of atoms/unit length of line)