Part-5+XRD(2)+theory(2018)+CP.ppt

In particular describe how you obtain necessary

Info icon This preview shows pages 49–56. Sign up to view the full content.

In particular describe how you obtain necessary information. [2]. Applying [1], theoretically calculate the diffraction intensities for Ge using a Cu-K a line, and make a plot of relative intensities of XRD pattern. Find necessary information to solve this question. [3]. Theoretically calculate the diffraction pattern for CaO using a Cu-K a line. (a) What is the crystal structure for CaO? (b) Derive simplified expressions for the structure factor F for CaO in terms of h, k and l . (c) Find the lattice constant of CaO from the ionic radius. (d) List the first five diffraction lines based on the structure factor of CaO derived in (b). (e) Plot atomic scattering factors for calcium and oxygen ions as a function of sin / . Note: use appropriate form of the valence state for calcium and oxygen in CaO form. (e) Calculate the theoretical intensity of the diffraction peaks for (c). (f) Make a plot of the calculated X-ray diffraction intensity with diffraction angle. (g) The diffraction pattern from CaO powder is shown bellow. Compare your calculated pattern with the experimentally determined pattern shown bellow.
Image of page 49

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Relative to a lattice point the centre of atom  j  of the basis is  R  = x j a  + y j b  + z j c   NaCl structure ZnS structure CsCl structure Primitive cubic lattice Face  centred cubic lattice Lecture 4 Basis: 1/2,1/2,1/2 0,0,0 Basis: 1/2,1/2,1/2 0,0,0 Basis: 1/4,1/4,1/4 0,0,0
Image of page 50
u, v, w = 0,   0,    0               1/2,1/2,1/2 CsCl structure   versus  BCC structure   1st             2nd
Image of page 51

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Basis: 1/4,1/4,1/4 0,0,0
Image of page 52
Structure factors for  diamond  and  zincblende  structures Diamond: Two FCC interpenetrated with the second FCC originated at (1/4, 1/4, 1/4) position (same kind of atoms) Zincblende: Two FCC interpenetrated with the second FCC originated at (1/4, 1/4, 1/4) position, but different kind of atoms 4-atoms 4-atoms 4-atoms 4-atoms
Image of page 53

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Diamond Structure and  Zincblende Structure   (Two ways of setting atom positions in order to compute structure factor) Procedure-1 Procedure-2 • Using lattice translation  basis • 1st FCC lattice originating from ( 0 0 0) • 2nd FCC lattice originating from ( 1/4 1/4 1/4) 1st FCC atom positions 2nd FCC atom positions 0        0        0  1/4     1/4    1/4 1/2   1/2       0  3/4     3/4    1/4 0      1/2      1/2                                  1/4      3/4    3/4 1/2     0      1/2 3/4      1/4    3/4 • Looking at the structure  very carefully • Find the atom positions that fill in 4-tetrahedral sites 1st FCC atom positions 4-tetrahedral sites 0        0        0   1/4     1/4    1/4 1/2   1/2       0  3/4     3/4    1/4 0      1/2      1/2                                  1/4      3/4    3/4 1/2     0      1/2 3/4      1/4    3/4 Which one do you prefer?    It is up to you!  
Image of page 54
How do you compute structure factor for Diamond?
Image of page 55

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Image of page 56
This is the end of the preview. Sign up to access the rest of the document.
  • Fall '12
  • p
  • Diffraction, Neutron diffraction, X-ray scattering techniques

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern