X-ray crystallography - CH8

Home > Flashcards > Print Preview

The flashcards below were created by user kevindevriendt on FreezingBlue Flashcards. What would you like to do?

  1. What are different analytical techniques that geologists use to identify minerals?
    • Petrographic microscopes
    • electron microscope
    • scanning electron microscope
    • mass spectrometer
  2. Explain the basic physics of XRD
    • - Free electons produced by heating a (cathode) filmaent, accelerated and strike a target (typically copper)
    • -When the electon hits the target, X-rays produced.
    • -These X-rays, after filtered, monochromatic X-rays are then directed towards the sampleof interest
    • the x-rays are then diffracted from parallel planes of atoms
  3. Why are X-rays diffracted by minerals?
    • -Caused by X-rays hitting parallel planes of atoms
    • -the rays 1 and 2 impinge on layers of atoms that are distance d apart
    • -
  4. What is Braggs law? What does the diagram look like?
    • this law demonstates that interference effets are observable only when radiation interacts with physical dimensions that are apporximately the saem size as the wavelentgth of the radiation
  5. What is d-spacing?
    distance between planes of atoms in a crystle structure
  6. why do peaks of different minerals have diferent position and intensities
    Intensity of peaks depend on number and kind of atoms present along a plane

    position of peaks depends on size and symmetry of a unit cell
  7. how is powder X-ray diffraction used to identify a mineral?

    What do peak intensities show?
    finely grounded powder packed into a sample holder, grain size <0.0704mm

    powderis used so that the specimen contains a veyr large number of tiny randomly oriented crystals. (not good for micas)

    • -use copper x-ray radiation
    • -run deterctor through a 2¬†angle between 5 dgrees and 70 degrees
    • - peaks in intensitiy indicate that the mineral possesses atomic planes who d-spacing is appropriate to "reflect" X-rays for that particular angle \theta1
  8. Why is powder X-ray diffraction used?
    The crystal must be correctly orientated, so powder methd is good because grains are all in different orientations

Card Set Information

X-ray crystallography - CH8
2012-10-08 16:20:22
ray crystallography

X-ray crystallography
Show Answers:

What would you like to do?

Home > Flashcards > Print Preview