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Accuracy in single-crystal x-ray diffractometry : influence of atmospheric pressure, scan mode and crystal settlement on intensity profiles
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| Abstract |
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| Simple statistical analysis of time series of intensity control reflections leads to: (i) quantitative description of the influence of atmospheric pressure on X-ray intensity measurements, which supplies arguments not to optimize an experimental instability factor p in the least-squares analysis, as is sometimes practised. (ii) the detection of scan mode (omega vs omega/2-theta) as a factor in the reproducibility of reflection profiles. The distribution of profile gravity centers revealed a random alignment error due to tolerance in diffractometer gear-wheels and a systematic one due to friction in the same parts during movements, (iii) a sensitive test to detect small movements (settlements) of the crystal during the data collection. It allows to omit dedicated orientation control measurements, using instead the profiles of intensity control reflections to trigger a re-orientation procedure, (iv) the recognition of severe limitations to fit observed profiles onto "learned" ones and of limitations in the precision of cell dimension determinations. | | |
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English
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| Source (journal) |
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Bulletin des sociétés chimiques belges. - Bruxelles | |
| Publication |
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Bruxelles : 1992
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0037-9646
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101:1(1992), p. 5-13
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| ISI |
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A1992HB16800002
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