Aluminium (or aluminum; see spelling differences) is a chemical element in the boron group with symbol Al and atomic number 13. It makes up about 8% by weight of the Earth's solid surface. The crystal structure of aluminium is face-centered cubic(FCC), and the atomic packing factor of face-centered cubic lattice is known to have the highest theoretical atomic packing factor than any lattice. Then in a face-centered cubic lattice, what is the theoretical atomic packing factor?