ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The variance of X-ray intensities is W = Σ2 + (k - 1)S2 - ΣiQi|fi|4, where Σ is the sum of the squares of the moduli of the atomic scattering factors fi, S is the modulus of the sum of the squares of the atomic scattering factors, k is 1 for noncentrosymmetric crystals and 2 for centrosymmetric, Qi is an integer depending on the space group and Wyckoff position, and the summation is over the atoms of the asymmetric unit. Values of Qi for the general reflexions and general positions are tabulated for the line, plane and space groups; they tend to be moderately positive for the less symmetric space groups and large and negative for the more symmetric. Special reflexions and special positions are discussed briefly. Dispersion shows itself in the distinction between Σ and S and in the modulus signs in the final term.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739478002028
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