材料科學(xué)基礎(chǔ)英文版課件_(11)-文庫吧
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【正文】 stal structures (3) Two other features: coordination number (CN) and atomic packing factor (APF) CN: the number of nearestneighbour atoms – 12 for FCC APF: the fraction of atomoccupied volume in a unit cell APF = (atomoccupied volume in a unit cell)/(unit cell volume) For FCC crystals: 4 atoms in a unit cell atomoccupied volume = 4?(4/3)(?R3) = 4?(4/3)?(?(a?2/4)3 = unit cell volume = a3 APF = atomoccupied volume/unit cell volume = Some mon metals: Al, Ni, Au, Cu, and Mn Metallic crystal structures (4) Interstices in FCC structures: octahedral interstices and tetrahedral interstices Ro = (a – 2R)/2 = (2?2R 2R)/2 = (1/2,1/2,1/2) Rt = ?3a/4 – R = (?3/4)? 2?2R) – R = (1/4,1/4,1/4) Diagonal length: ?3a
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