CHEM 123: Practice Problems page 1of30B1.Simple cubic packing.The crystal lattic and unit cell for simple cubic packing are shown below.a)# spheres = ()()18sphere/corner8 corners= 1 sphereb) The coordination number of each sphere is 6. To see this, focus on an “interior” sphere such as sphere “A” in the figure on the left. That sphere is in contact with 6 other spheres – the one above it, the one below, the one in front, the one behind, the one to its left and the one to its right. c)If the radius of each sphere is “R” then the edge length of the unit cell is a= 2Rd) The volume of the unit cell is Vcell= a3= 8R3 There is one full spherecontained within the unit cell so the volume of spheres contained within the unit cell is 3spheres43VR=π. 34330.523668spherescellVRPackingEfficiencyVRππ====A
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