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SUBJECT:CRYSTAL STRUCTUREGUIDANCE BY:-ANIL SIRNAME:RATHOD VISHAL.ENROLLMENT NO:140950119066

SEM:3DEPARTMENT OF MECH. ITM UNIVERSE

Crystal StructureBCC FCC

HCP

rhombohedral a = b = c simple rhombohedral = = 90 oCrystal systemonly 7 different types of unit cells14 standard (Bravais) unit cells coulddescribe all possible lattice networkscrystal axial lengths &system interaxial angles space latticecubic a = b = c simple cubic = = = 90 o body-centered cubicface-centered cubictetragonal a = b c simple tetragonal = = = 90 o body-centered tetragonalorthorhombic a b c simple orthorhombic = = = 90 o body-centered orthorhombicbase-centered orthorhombicface-centered orthorhombicmonoclinic a b c simple monoclinic = = 90 o base-centered monoclinictriclinic a b c simple triclinic 90 hexagonal a = b c simple hexagonal = = 90 o = 120 o

Metallic crystal structures90% elemental metals crystallize into threecrystal structures: body-centered cubic (BCC)a (nm) R (nm)Cr 0.289 0.125Fe 0.287 0.124Mo 0.315 0.136K 0.533 0.231Na 0.429 0.186Ta 0.330 0.143W 0.316 0.137V 0.304 0.132hexagonal close-packed (HCP)a c (nm) R (nm)Al 0.2973 0.5618 0.143Zn 0.2665 0.4947 0.133Mg 0.3209 0.5209 0.160Co 0.2507 0.4069 0.125Zr 0.3231 0.5148 0.160Ti 0.2950 0.4683 0.147Be 0.2286 0.3584 0.113face-centered cubic (FCC)a (nm) R (nm)Al 0.405 0.143Cu 0.3615 0.128Au 0.408 0.144Pb 0.495 0.175Ni 0.352 0.125Pt 0.393 0.139Ag 0.409 0.144

coordination number = 8total 2 atoms per unit cell4 R3 a = 4 R a = 3atomic packing factor (APF)volume of atoms in unit cellAPF = volume of unit cellAPF = 0.68

FCC

coordination number = 12total 4 atoms per unit cell4 R2 a = 4 R a = 2APF = 0.74the closest packing possible of sphericalatoms cubic closest-packed

HCPcoordination number = 12total 2 atoms per unit cellAPF = 0.74the closest packing possible of sphericalatomsc/a ratio for ideal HCP structure is 1.633

ITM STUDENT

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