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quiz2fall2000

# quiz2fall2000 - -as drawn ~ x 5 Calculate the density of...

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ENGSC 3313, Fall 2000 Quiz 2 Name Answer anI 4 guestions onlI, 1 point each A cube has 9 planes of symmetry .Explain ! I. 1016 Bisect each face with planes parallel to the cube sides, and also planes through the face diagonals. Giving 3 and 6 symmetry planes respectively, total 9. 1 2. Calculate the plane's density of a {110} plane for a BCC metal. Taking the atoms to be spheres in contact, the plane's density would be the fraction of the total plane area that is occupied by atoms. a 0 =~ Draw the plane (310) and the direction [121] in a cubic unit cell. 3 z For ~lanes, we use reciprocals. Intercepts are thus, -1/3, 1, 00 , hence the sketch. For directions, dividing by 2 to keep in 1 cell, we go 1/2, then I, then -V2. ~ ~ I I I I I I I I /-~?

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z y The 'c' value is fixed as it is not equivalent the others. Hence, our possibilities are [012], [012] , [102], 102] --as drawn.
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Unformatted text preview: --as drawn. ~ x 5 Calculate the density of the PCC compound, LiP. The ionic radii are 0.068 and 0.133 nm, respectively. Avagadro's number is 0.6022 x 1024; the amu are 6.94 and 19.00 for Li and P, respectively. Express your answers as g!cm3 or Mg!m3. Mass of Unit Cell Density = Volume of Unit Cell FCC compound, hence 4 of each per cell and 2R + 2r = a Hence, D = 4(6.94 + 19.00)/0.6022 x 1024 23(0.068 + 0.133? x 10-27-the 10-27 is (nmf to m3 D -W Mg/m3 6 Calculate the packing factor of CsCI. The ionic radii are Cs = 0.169 nm and CI = 0.181 nm. Recollect that CsCI does J1Q.1; have the same structure as NaCI (or LiP)! One kind of ion is at the cell comer, the other at the cell center. There is, on average, one of each type per cell The contact along the cube diagonal, so 2R + 2r = . .[ja...
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quiz2fall2000 - -as drawn ~ x 5 Calculate the density of...

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