图 六排密方 a hexagonal (a) (b) HCP center of atom at 211 33 Hexagonal close-packed center of atom located in next unit cell 12of an atom (c) 1 材料科学与工程学院 6 of an atom 8 School of Materials Science and Engineering材料科学与工程学院 School of Materials Science and Engineering 8 (c) (a) (b) hexagonal c a center of atom located in next unit cell center of atom at       2 1 , 3 1 , 3 2 of an atom 12 1 6 of an atom 1 六排密方 HCP Hexagonal close-packed