1,330
edits
R-factors: Difference between revisions
no edit summary
No edit summary |
No edit summary |
||
| Line 39: | Line 39: | ||
We can plot (Diederichs <ref name="Di06">K. Diederichs (2006). Some aspects of quantitative analysis and correction of radiation damage. Acta Cryst D62, 96-101 [http://strucbio.biologie.uni-konstanz.de/strucbio/files/Diederichs_ActaD62_96.pdf]</ref>) | We can plot (Diederichs <ref name="Di06">K. Diederichs (2006). Some aspects of quantitative analysis and correction of radiation damage. Acta Cryst D62, 96-101 [http://strucbio.biologie.uni-konstanz.de/strucbio/files/Diederichs_ActaD62_96.pdf]</ref>) | ||
<math> | <math> | ||
R_{d} = \frac{\sum_{hkl} \sum_{|i-j|=d} \vert I_{hkl,i} - I_{hkl,j}\vert}{\sum_{hkl} \sum_{|i-j|=d} (I_{hkl,i} + I_{hkl,j})/2} | R_{d} = \frac{\sum_{hkl} \sum_{|i-j|=d} \vert I_{hkl,i} - I_{hkl,j}\vert}{\sum_{hkl} \sum_{|i-j|=d} (I_{hkl,i} + I_{hkl,j})/2} | ||
</math> | </math> | ||
which gives us the average R-factor of two reflections measured d frames apart. As long as the plot is parallel to the x axis there is no radiation damage. As soon as the plot starts to rise, we see that there's a systematical error contribution due to radiation damage. | which gives us the average R-factor of two reflections measured d frames apart. As long as the plot is parallel to the x axis there is no radiation damage. As soon as the plot starts to rise, we see that there's a systematical error contribution due to radiation damage. | ||
| Line 51: | Line 51: | ||
=== Comparing two sets of structure factor amplitudes or intensities === | === Comparing two sets of structure factor amplitudes or intensities === | ||
The following is symmetric, and suitable for comparing two data sets, or two model amplitudes: | The following is symmetric, and suitable for comparing two data sets, or two model amplitudes: | ||
<math> | <math> | ||
R=\frac{\sum_{hkl}\vert F_{hkl}^{i}-F_{hkl}^{j}\vert}{\sum_{hkl} 1/2 (F_{hkl}^{i}+F_{hkl}^{j})} | R=\frac{\sum_{hkl}\vert F_{hkl}^{i}-F_{hkl}^{j}\vert}{\sum_{hkl} 1/2 (F_{hkl}^{i}+F_{hkl}^{j})} | ||
</math> | </math> | ||
for amplitudes, and analogously for intensities: | for amplitudes, and analogously for intensities: | ||