Detection and Correction of Systematic Errors

The calibration curve is used to correct 20-values of a sample that was measured under the same conditions as the standard (external standard). Some errors, especially the sample position and the transparency error, differ from 

after some time the at-first amorphous oxide-skin becomes crystallized. 

For smaller angles a synthetic fluorphlogopite, KMg3[Si3A10io/F2], is available as SRM 675 with i/ooi = 9-98104(7) A at 25 °C (Table 4.9). This mica material should possibly be oriented parallel to the sample surface (strong 

For powders of rock samples quartz offers itself as a natural standard, especially because quartz is a rather pure compound with approximately constant lattice constants (Table 4.10). Natural calcite often contains Mg in solid solution with decreased lattice constants and is less suited as standard. Furthermore, calcite exhibits a negative temperature coefficient in the u-direction. 

As secondary standards for the calibration of d-values the following compounds are used  

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Flack, H. D. Avoidance, detection and correction of systematic errors in intensity data. In Crystallographic Computing 3 Data Collection, Structure Determination, Proteins and Databases. (Eds., Sheldrick, G. M., Kruger, C., and Goddard, R.) pp. 3-17. Clarendon Press Oxford (1985). 

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