RSCAN : Analyse R-factors

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`RSCAN` : Analyse R-factors

Authors: George Davenport and Syd Hall

Contact: Syd Hall, Crystallography Centre, University of Western Australia, Nedlands 6907, Australia

RSCAN analyzes structure factor residuals and ratios in terms of Miller indices, measured structure factors, measured intensities (if present on the bdf), and (sin $\theta$ / $\lambda$ ) $^{2}$ . RSCAN calculates multiplicative corrections to scale factors, the thermal displacement parameter shift, and the overall R-factor. It is an adaptation of the XRAY program RLIST (Hall, 1972).

Program Calculations

Data are accumulated separately for reflections with rcode=1 and rcode=2, for each of the six quantities h, k, l, measured F, $s^{2}$ , and measured I. Parameters on the RSCAN line are used to determine the range and the interval size for each quantity.

h, k, l

Each interval is a single integer value. The range is from -N to +N, as specified on the maxhkl line.

F(rel)

The range is divided into two sub-ranges. The first goes from 0 to max1 with intervals of uniform size int1. The second goes from max1 to max2 with intervals of size int2. The defaults for max1, max2, int1 and int2 are 19.0, 500.0, 1.0, and 10.0, respectively.

sin $\theta$ / $\lambda$ (s)

The range extends from a value of 0 to the maximum value with intervals of uniform size.

I(rel)

The range extends from 1 to a maximum. The interval boundaries are determined by the factor on the RSCAN line. The boundaries are 1.0, factor, factor $^{2}$ , ... , up to the specified maximum. Note that R-factors for I(rel) will be calculated only if the I(rel) is present in the bdf. Note also that factor must be greater than 1.0.

Calculated Quantities

For rcode=1 and for rcode=2, for each of the six quantities, for each interval, the following quantities are determined. All reflections with rcode>2 are ignored.

Number of reflections within that interval
Mean value of F(rel) for reflections within that interval
Mean value of F(cal) for reflections within that interval
Mean value of F(cal)/F(rel) for reflections within that interval
Mean value of |F(rel)-F(cal)| for reflections within that interval

File Assignments

Reads reflection data from the input archive bdf

References

Hall, S.R. 1972. RLIST. The X-RAY System of Crystallographic Programs for any Computer TR-192, 223.
Wilson, A.J.C. 1942. Determination of Absolute from Relative X-ray Intensity Data. Nature 150, 151.