BAD 200 Lecture Notes - Lecture 6: Lattice Constant
18 Dec 2020
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1 host = fcc impurity = nevc za =4r 2012r la size of - (v2-1) = 0. 414 r octahedral void 1 r = 0. 414r - r- ra host atom rading impurity void radius. Va=r+y fua ba structure ba=4r = arute w =rty = --[-]r [[ zoo298] lattice parameter of free 4 ratza. R = 120 octahedral vaid size in foc y = 0. 414 swastinte de octankatral. In fee (r=0. 414 ( xa) nm tetray a in. Bcc [rzooza ( xa ) none weert ve von because : * * octahedral void is a symmetric void in ice but in bcc it is not symmetric. In order to accomodate a impurity atom stresses of by surrounding atoms should be symmetrical otherwise it is impossible. That why in bcc - tetrahedral void is lage - and accomodate vory less. But fcc - octahedral void produces sery small kiltice distactions askile accomodate * * symmetric. Asymmetric = low lattice distortion = high lattice distortion.
