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Some Comments on Rint

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# Some Comments on Rint - PowerPoint PPT Presentation

Some Comments on Rint. For a good crystal Rint is < 10% For even a bad crystal Rint<20% For a good crystal the % of data removed is <1.5% For a bad crystal <8%. Very Large Values. Sometime get very large values for both Rint and % removed.

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## Some Comments on Rint

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Some Comments on Rint
• For a good crystal Rint is < 10%
• For even a bad crystal Rint<20%
• For a good crystal the % of data removed is <1.5%
• For a bad crystal <8%
Very Large Values
• Sometime get very large values for both Rint and % removed.
• This always means you are in the wrong crystal class
• Example monoclinic with beta = 90
• Tetragonal that is orthorhombic
Data Reduction
• The data measured is inensity
• It needs to be converted to Fobs or Fobs2
• There are two corrections.
• Polarization –because x-ray beam is not polarized and diffraction is not in plane of polarization =(1+cos22q)/2
• Lorenz Factor is a function of the instrument type and setup
• |F|=(I/Lp)1/2
What have we done so far?
• Found and mounted a crystal
• Checked its quality
• Determined the unit cell
• Collect a set of frame data
• Integrated the frames
• Scaled the frames—combined equivalent reflections
• Reduced the data
• Formatted the data
What is next for the data
• Correct for absorption if needed
• Integrated absorption correction
• Empirical absorption correction
• A “fudge” correction later
• If we are going to do a correction a file containing direction cosines on unaveraged data is required
• Correct for decay if needed