Xray Powder Polycrystalline Diffraction on the BRUKER SMART 1000 CCD

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X-ray Powder (Polycrystalline) Diffraction on the
BRUKER SMART 1000 CCD
Joseph H. Reibenspies X-Ray Diffraction
Laboratory Texas A M University College
Station, Texas
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The Problem

• The problem with single-crystal X-ray
  diffraction is the single-crystal!
• The structure that is determined is actually the
  structure seen in that single-crystal!
• Is the structure of the single-crystal the
  structure of the bulk sample ?

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The Conformational Isomer Problem CYCLEN

• CYCLEN (C8H16N4 Hx) 12 member ring with over 18
  allowed conformational isomersa.

4 known molecular structures of CYCLEN
aDale, J. Acta Chem. Scand. (1973) 27, 115-1129.
Meyer, M. et.al Coord. Chem. Rev. (1998)
178-180, 1313-1405.
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The Powder Preparation Problem

• Not all compounds are accommodating to powder
  work.
• Grinding, packing and sieving can effect the
  powders structure
• Some samples show preferred-orientation (texture)

We need non-obtrusive, non-destructive and
convenient procedure to prepare the powder, that
is closest to the conditions of the
single-crystal experiment.
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Sample Preparation in Apiezon Grease
1. Place crystals in grease on slide
2. Grind Crystals to fine powder.
3. Mount powder/grease on glass fiber
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The Powder Data Collection on the SMART 1000.

• Molybdenum Radiation (?0.7109Å) (1024
  resolution)
• The detector is set to a reproducible position
  (e.g. the
  first stop in the dove tail 14.55cm)
• Mount a standard and calibrate swing angle,
  specimen to detector distance and beam/detector
  intersection. (Silicon powder 12.989o, Mo)
• Mount specimen and optically align. Specimen
  should be 0.3 mm in diameter or in a 0.3mm
  capillary (0.5mm beam)
• Collect rotation frame with swing angle at the
  zero position. (good Debye rings should be
  visible, if not re-grind)
• Drive swing angle to 10o (or -10o) on 2? and
  acquire rotation photo (uncheck Zero option).
  Take long exposure (1200 sec) against appropriate
  dark current.
• Save un-warped frame (interpolated data).

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Silicon Standard
Mo ? 0.7109Å K?1 Calibration with
Silicon Sample Detector 3.0cm
Calibration with Silicon Sample Detector
14.55cm Swing Angle 10.0o (2?) Pixel center
507x , 504y First ring at 12.989o (2?)
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Data Processing in GADDS.

• Load standard frame and calibrate.
• Confirm known 2? positions of the standard.
• Load data frame. If more than one frame is to be
  added use the LOAD command.
• Integrate (chi option) frame cone and save as a
  PLOTSO file. Adjust cone to include as much of
  the frame as possible
• In the PEAKS option, manually select peaks.
• Run XPOW for simulation with known data set or
  molecular structure (XFOG).
• Calculatea

• Fn gt 20 is a good match

aJenkins Synder Introduction to X-ray Powder
Diffractometery pp 315.
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The CYCLEN Powder Pattern
a) GADDS, Bruker AXS, Madison, WI b)POWDERX,
Cheng Dong, Institute of Physics, Chinese Academy
of Sciences, P. O. Box 603, Beijing 100080,
e-mail chengdon_at_aphy01.iphy.ac.cn c) SHELXTL
5.0 Bruker AXS, Madison, WI
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Powder Pattern Peaks for CYCLEN
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Sample Preparationa
aSmith, D.K. Barrett, C.S. Adv. X-ray Anal.
(1979) 22, 1-18.
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Grindinga
Better Grinding
Poor Grinding
Good Grinding
Textured Sample
aBish D.L. Reynolds, R.C. Modern Powder
Diffraction Bish Post Eds. pp73-78.
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Dry Powder Preparation
Capillary
Hair Spray
Loops
Rubber Cement
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The Binder and The Background
a0.3mm thickness all materials
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Transmission vs Reflection
Transmission Modea
Reflection Modeb
aDecker, B.F., Asp, E.T. Harker, D. J. Appl.
Phys. (1948) 19, 388-392. bSchultz, L.G. J. Appl.
Phys. (1949) 20, 1030-1033.
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Dark Currents are Important

• Turn smoothing routines off before collecting the
  dark current.
• Long exposures are effected the most by hot
  specs.

Fly specs! The hot pixel problem!
Air scattering with smoothed and un-smoothed dark
currents
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Background Subtraction in GADDSa
Fe(NH4)2(SO4)2 6H2O
aJenkins Synder Introduction to X-ray Powder
Diffractometery pp 297.
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Micro-Samplesa
Fe(NH4)2(SO4)2 6H2O
A single crystal of the sample was placed on the
NaCl and ground. (100 ?g)
aBish D.L. Reynolds, R.C. Modern Powder
Diffraction Bish Post Eds. pp93-97.
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Gold Plating on Brass Pina
Brass
Information Depth
Metal Two-theta (?0.7109).... Au 17.46 20
.02 CuSn 19.57 22.25 31.66 37.57
Au
aBunge, H. Defect and microstructure Analysis
by Diffraction Synder, Fiala, Bunge eds.
pp411-519. Iyengar, S.S. et.al. Adv. Xray Anal.
(1986) 30, 457-464.
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Back (side) Diffraction
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Comparison of Fe(NH4)2(SO4)2 6H2O powder patterns
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Its all Relative
Acknowledgements Bruker AXS -Uwe
Preckwinkel - Brian Litteer - Arnt Kern -
K. Smith TAMU - X. Ouyang - A. Clearfield -
R. Motekaitis
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