2. Crystal Structure

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direction indices in HCP unit cellfour indices [uvtw] u + v + t =0u = ⅓(2u – v) v = ⅓(2u – v) t = -(u + v)directions a 1 , a 2 , a 3+a 3 direction incorporating c axisdirections on the upper basal planes14
volume, planar, linear densityvolume densitymass/unit cellρ v = ————————volume/unit cellex. Cu has FCC structure, atomic radius of0.1278 nm, atomic mass of 63.54 g/molcalculate the density of Cu in Mg/m 3 .FCC structure √2 a = 4 Ra = 2 √2 R = 2 √2 (1.278 × 10 -10 )= 3.61 × 10 -10 mV = (3.61 × 10 -10 m) 3 = 4.70 × 10 -29 m 34 Cu per unit cellm = 4 × 63.54 × 1.66 × 10 -30 Mg = 4.22 × 10 -28 Mgρ v = 4.22 × 10 -28 Mg / 4.70 × 10 -29 m 3= 8.98 Mg/m 3 (exp. = 8.96 Mg/m 3 )planar atomic densityequiv. no. of atoms whose centersare intersected by selected areaρ p = ————————————selected areaex. calculate planar atomic density ρ p on (110)plane of the α-Fe in BCC lattice inatoms/mm 2 . (lattice constant a = 0.287 nm)15
Page 2: crystal systemonly 7 different type
Page 5 and 6: BCCFCCcoordination number = 8total
Page 7 and 8: the closest packingHCPa b a b a …
Page 9 and 10: directions are crystallographically
Page 11 and 12: ex. draw the following crystallogra
Page 13: hexagonal structureMiller-Bravais i
Page 17 and 18: no. of atoms = ½ + 1 + ½ = 2 atom
Page 19 and 20: X-ray diffractionreflected wave pat
Page 21 and 22: diffraction pattern for cubic unit
Page 23: BCC {110) and {200}sin 2 θ A h 2 A

2. Crystal Structure

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