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2409 articles match your search "weighting scheme"Results 1 to 10, sorted by relevance:
research papers
A weighting scheme for the X-ray restrained/constrained wavefunction approach is proposed. Test calculations were carried out with both theoretical and experimental X-ray diffraction data to assess advantages and drawbacks of the proposed approach in the different cases.
research papers
In paper I of this series [Giacovazzo (1979). Acta Cryst. A35, 757-764] a tangent formula was obtained which is able to take into account uncertainty of the 'known' phases. In paper II [Cascarano, Giacovazzo, Burla, Nunzi & Polidori (1984). Acta Cryst. A40, 389-394] the asymptotical distribution of the statistic αh was derived when the r component vectors Gj exp (iθj) were distributed according to Von Mises distributions M(θj; φh, Gj). In the present paper this result is extended to the case in which the vectors Gj exp (iθj) are distributed according to a more general distribution M(θj; φh, βj). From the theoretical results a weighting scheme for the tangent procedure is derived which uses the first two moments of the αh distribution. The scheme has been implemented in the SIR program; applications to real structures are presented.
research papers
A new weighting scheme for the minimization function used in the Rietveld method for structure refinement using powder diffraction data is proposed. It significantly improved the accuracy of positional parameters of test samples.
computer programs
Open access
A new standalone program to calculate optimized values for weighting parameters, CAPOW, is presented along with enhanced visualization tools for analysing statistical distributions of data.
research papers
The limitations of weighting between the sum of chemical and data-based targets in macromolecular crystallographic refinement based on comparing the gradients or Hessian diagonal terms of the two potential functions are demonstrated, especially in the context of a maximum-likelihood target that is inherently weighted by the model and data errors
research papers
A new method for pole figure measurement is described, entitled a dynamic segmented spiral scheme. This scheme provides a promising alternative to conventional methods of simultaneous texture and phase fraction measurement.
research papers
It is demonstrated that, by inputting the reflection data in an incremental fashion starting with low- and medium-resolution reflections, the convergence rate of the hybrid input–output ab initio phasing algorithm can be significantly increased.
short communications
The truncated Chebyshev polynomial provides a reliable scheme for the automatic determination of empirical weights for least-squares structure refinement when the errors are a function of |Fo|.
research papers
Open access
A simple weighting scheme for macromolecular refinement that is robust with respect to an incomplete atomic model is discussed.
research papers
One-line and two-line empirical weighting schemes, as a function of sinθ/λ, are shown to be superior to the unit weights or experimental weights for the refinement of protein structures. Improvements are noted in the figures of merit as well as in the stereochemistry of the resulting model.