Crystal structure of solidsMechanical Engineering Departmen 机械工程系固体的晶体结构

12/7/2021Crystal structure of solids12/7/2021AgendauReviewuSpace latticeuLattice parametersuUnit cellu7 crystal structuresu14 Bravais lattices12/7/2021ReviewuQuick review of previous classnAtomic structurenAtomic bondsnStructure of solidsSOLIDStrong bondingLong range order12/7/2021Space latticeu3D regular arrangement of points in spaceuHow can the atomic arrangement in solids be mathematically described?uIn two dimensionsXYXYgababg(a) in a Cartesian system(b) in a general system12/7/20213D Space LatticeXYZabcbga12/7/2021Lattice parametersuTo define any lattice 6 lattice parameters are neededua, b, c,(sides) a, b, g,(angles)uHow many unique space lattices can be derived?Only 7 such lattices can be derivedWhen atoms are placed on the lattice points we get CRYSTAL STRUCTURES12/7/2021Unit celluBasic building block in the generation of a space latticeabcgba12/7/2021This (corner of the cube) point is shared by eight unit cells.Therefore only one-eighth of the point belongs to each unit cell.12/7/20217 crystal structures12/7/202114 Bravais latticeswTriclinicPwMonoclinicPCwRhombohedralPwOrthorhombicPIFCwTetragonalPIwHexagonalPwCubicPIFP=primitiveI=innenzentric (body centered)F=face centeredC=base centered12/7/2021An example12/7/2021SummaryuSpace latticeuLattice parametersuCrystal structuresuBravais lattices12/7/2021PreviewuCubic systemuSimple cubic (SC)uBody centered cubic (BCC)uFace centered cubic (FCC)uMiller indicesuHexagonal system