X-ray Crystallography - The Beginning

2. X-ray Crystallography - The Beginning Diffraction: A systematic, cooperative scattering of rays by an interfering array. The spacing of the elements of the array must be of the same order of magnitude as the wavelength of the rays.

3. 1912 - Max von Laue: German Mathematician, Chemist, Physicist and Nobel Prize winner. X-rays might diffract off of atomic lattice planes, like light diffracts from a diffraction grating.

4. 1912 University of Munich, Germany Walter Freidrich Paul Knipping Sphalerite = ZnS

5. LAUE CAMERA

7. FOR THE FIRST TIME: 1. It proved that there was an ordered internal atomic arrangement within crystalline substances 2. The atoms were spaced in regular arrangements (arrays) on the order of magnitude of size as the wavelength of X-rays.

8. Laue Pattern TETRAGONAL

9. Precession Camera

10. Precession Camera Tetragonal

11. 1913 - 1914 William Henry Bragg and William Lawrence Bragg Father and Son English Physicists BRAGG’S LAW: nλ = 2 d Sin Θ λ = wavelength of X-rays n = any whole # d = spacing between atomic planes in angstroms Θ = angle of X-ray incidence on atomic planes

12. http://epswww.unm.edu/xrd/resources.htm See: Braggs Law and Diffraction; “Details”

14. Constructive and Destructive Interference of waves by a regularly spaced array.

15. THE X-RAY DIFFRACTOMETER AND OTHER XRD INSTRUMENTATION

16. INSTRUMENTATION: XRD POWDER DIFFRACTION Generator 40,000 to 50,000 volts 30 to 20 milliamps Tube Rating: 2100 watts Run at 80% Water Chiller 1 liter/min flow rate 65 degree F temperature. X-ray Tube: Cu - target Mo also used Mo = 0.7107 λ K alpha avg Cu = 1.5418 λ K alpha avg Cr = 2.2909 λ K alpha avg

19. Bremstrahlung: "Breaking Radiation" Most common Scenario: High Energy Electrons have only a distant encounter. Small amount of Energy lost. Less than common Scenario: High Energy Electrons have a near encounter. Moderate amount of Energy lost. Uncommon Scenario: The High Energy Electron experiences a head on collision. Gives up just about all of its kinetic energy .

23. Characteristic X-rays

24. Monochromator: Absorption Edge Filters Cu Target Ni Filter Mo Target Zr Filter Cr Target V Filter Graphite Monochromater Goniometer: Sollar Plates - Divergent Slit - Sample - Receiving Slit - Sollar Plates - Scatter Slit - Detector Detector Scintillation Detector Theta - Two Theta Rotation

26. Monochromator: Absorption Edge Filters Cu Target Ni Filter Mo Target Zr Filter Cr Target V Filter Graphite Monochromater Detector Scintillation Detector Theta - Two Theta Rotation Goniometer: Sollar Plates - Divergent Slit - Sample - Receiving Slit - Sollar Plates - Scatter Slit - Detector

30. XRAY DIFFRACTION DATA BASE OF INORGANIC AND ORGANIC CRYSTALLINE SUBSTANCES • I.C.D.D. International Centre for Diffraction Data • Swathmore, Pennsylvania • J.C.P.D.S. Joint Committee on Powder Diffraction Standards • Hanawalt Search Method:

31. Debye-Scherrer Camera

35. POWDER CAMERA FORMULA Camera diameter: 114.6 mm Camera radius 57.3 mm S = (2  r)(4) S = distance between arc set 360  on powder film (mm)  = 3.1416  = angle of incident of X-rays on lattice planes d = atomic spacing between planes in Å  = 360 S = X-ray wavelength for Cu 4(2  r) target: 1.5405 Å n = Any whole number.  = (360) Smm = S 4(2) (3.1416) (57.3 mm) 4

36. Example Problem: Mineral species: Titanite [ CaTiSiO5 ] has a major set of planes with a 3.21Å d-spacing. A set of arcs measured from the film strip: S = 55.5 mm  = 360 S = (360) ( 55.5) = 55.5 = 13.87 4(2  r) 8 (3.1416) (57.3) 4 d = n  = 1.5405 = 1.5405 = 2 Sin  2 Sin (13.87) 2 (0.2397) 1.5405 = 3.2 0.4794 d = 3.2 Å