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Engr302Wk2-2 - California National University ENGR 302...

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California National University ENGR 302 Kathryn Toth Week #2 Assignment #2 2/23/11
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3.1) The difference between atomic and crystal structure is that not all atoms have a crystalline structure first of all, only crystalline solids. But they both are the arrangement of molecules. Atomic structures are not orderly and can actually seem random, whereas crystalline structures are orderly and repeated, making them predictable. 3.9) BCC: a= 4R3 V c = a3 = ρ nAVcNA V c = 4R3^3 = 64R39 n=2 16.6 g/cm 3 = ( . / ) × ( . ) 2 180 9g mol 964R3 6 023X1023atomsmol . 16 6gcm3 = . ( ) . 18180 9g mol mol64R36 023x1023atoms 16.6( ) R3 ∙atoms = . × - 8 447 10 23 ∙cm2 = . × - / R3 5 089 10 24cm3 atom = . / R3 0 005089nm3 atom R = 0.172 nm 3.47)
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a) Orthorhombic b) FCC c) 18.91 g/cm 3 = 1.891 × - / 10 20g nm3 = ρ nAVcNA A= ρVCNAn n=4 = . . . = . VC 0 39nm0 3nm0 25nm 0 029nm3 A= . × - . ( . × ) 1 891 10 20gnm30 029nm3 6 023 1023atomsmol 4 A=82.57 g/mol 3.65) a/b) Peak 1) Assume : 2 θ =40 ° , n=1. We know that with the BCC, h,k&l are even. We know that the atomic radius of Tungsten is 0.137nm. = = . = . a 4R3 40 137nm3 0 316nm = dhkl nλ2sinθ = ( . ) ° dhkl 1 0 1542nm 2sin20 dhkl =0.22nm
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= + + dhkl ah2 k2 l2 = h 2 +k 2 +l 2 = (. . 316nm0 22nm )^2= 2.06= 1 2 +1 2 +0 2 = (110)
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