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Friday, September 25, 2015

Body Centered Cubic Structure



Body-centered cubic unit cells have an atom in the center of the cube as well as one in each corner. The packing efficiency is 68%, and the coordination number = 8. Atoms touch each other along cube diagonals within a  unit cell. All atoms are identical.




ex: Cr, W, Fe (a), Tantalum, Molybdenum

                                    



Close-packed directions: length = 4R = sqrt (2a)
Unit cell contains:     6 x 1/2 + 8 x 1/8 = 4 atoms/unit cell 


 



Elements with monoatomic BCC structure