ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
A method for minimizing the variance in integrals and derivatives of electron densities by filtering the scattering amplitudes is established. The optimum filters for the density and its integrals and derivatives are shown to be the same. Calculations with experimental data show that the variance of integrated densities is not very sensitive to the shape of the region of integration, indicating that good estimates may be made using simple shapes. A very convenient expression is given for the variance of the integral over a sphere. Coppens & Hamilton [Acta Cryst. (1968), B24, 925-929] have shown that accurate estimates of integrated densities are possible. Filtering can further improve these estimates. By contrast, good estimates of derivatives of the electron density remain unlikely, even using filtered diffraction data.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739478001527
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