Powder Diffraction

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Lynne B. Mccusker - One of the best experts on this subject based on the ideXlab platform.

  • Electron crystallography as a complement to X-ray Powder Diffraction techniques
    Zeitschrift Fur Kristallographie, 2012
    Co-Authors: Lynne B. Mccusker, Christian Baerlocher
    Abstract:

    X-ray Powder Diffraction / HRTEM / SAED / PED structure solution Abstract. Electron microscopy techniques yield informa- tion for crystal structure analysis that is remarkably com- plementary to that obtained from X-ray Powder Diffraction data. Structures of polycrystalline materials that resist so- lution by either method alone can sometimes be solved by combining the two. For example, the intensities extracted from an X-ray Powder Diffraction pattern are kinematical and can be interpreted easily, while those obtained from a typical selected area electron Diffraction (SAED) or preces- sion electron Diffraction (PED) pattern are at least partially dynamical and therefore more difficult to use directly. On the other hand, many reflections in a Powder Diffraction pattern overlap and only the sum of their intensities can be measured, while those in an electron Diffraction pattern are from a single crystal and therefore well separated in space. Although the intensities obtained from either SAED or PED data are less reliable than those obtained with X- rays, they can be used to advantage to improve the initial partitioning of the intensities of overlapping reflections. However, it is the partial crystallographic phase informa- tion that can be extracted either from high-resolution trans- mission electron microscopy (HRTEM) images or from PED data that has proven to be particularly useful in com- bination with high-resolution X-ray Powder Diffraction data. The dual-space (reciprocal and real space) structure determination programs Focus and Superflip have been shown to be especially useful for combining the two dif- ferent types of data.

  • Chapter 9 – Product characterization by x-ray Powder Diffraction
    Verified Syntheses of Zeolitic Materials, 2001
    Co-Authors: Lynne B. Mccusker
    Abstract:

    Publisher Summary This chapter covers the different features of a Powder Diffraction pattern, which can be exploited in the characterization of a material. Powder Diffraction data is most commonly used as a "fingerprint" in the identification of a material, but the other information that can be gleaned from a Diffraction pattern should not be forgotten. If the pattern is to be indexed it is essential that the peak positions be determined accurately. In this case, the instrument's 2Θ scale needs to be carefully calibrated using a standard material such as the NIST silicon standard 640b. The sharper a peak, the better its 2Θ value can be determined, so the diffractometer should also be adjusted to optimize resolution. For indexing purposes, the intensities of the peaks are irrelevant, but for identification or for structure analysis, accurate relative intensities are essential. Most Powder Diffraction data analyses assume that the sample consists of millions of randomly oriented crystallites. If this is not the case, relative intensities will be distorted. In a zeolite laboratory, Powder Diffraction data are most commonly used to identify a newly synthesized material or to monitor the effects of a post-synthesis treatment.

  • Product characterization by x-ray Powder Diffraction
    Microporous and Mesoporous Materials, 1998
    Co-Authors: Lynne B. Mccusker
    Abstract:

    Publisher Summary This chapter covers the different features of a Powder Diffraction pattern, which can be exploited in the characterization of a material. Powder Diffraction data is most commonly used as a "fingerprint" in the identification of a material, but the other information that can be gleaned from a Diffraction pattern should not be forgotten. If the pattern is to be indexed it is essential that the peak positions be determined accurately. In this case, the instrument's 2Θ scale needs to be carefully calibrated using a standard material such as the NIST silicon standard 640b. The sharper a peak, the better its 2 Θ value can be determined, so the diffractometer should also be adjusted to optimize resolution. For indexing purposes, the intensities of the peaks are irrelevant, but for identification or for structure analysis, accurate relative intensities are essential. Most Powder Diffraction data analyses assume that the sample consists of millions of randomly oriented crystallites. If this is not the case, relative intensities will be distorted. In a zeolite laboratory, Powder Diffraction data are most commonly used to identify a newly synthesized material or to monitor the effects of a post-synthesis treatment.

Christopher J Gilmore - One of the best experts on this subject based on the ideXlab platform.

  • High-throughput Powder Diffraction V: the use of Raman spectroscopy with and without X-ray Powder Diffraction data
    Journal of Applied Crystallography, 2009
    Co-Authors: Gordon Barr, Christopher J Gilmore, Gordon Cunningham, Wei Dong, Takashi Kojima
    Abstract:

    In high-throughput crystallography it is possible to accumulate large numbers of Powder Diffraction patterns on a series of related compounds, often polymorphs, salts or co-crystals. In previous papers [Gilmore, Barr & Paisley (2004). J. Appl. Cryst. 37, 231-242; Barr, Dong & Gilmore (2004). J. Appl. Cryst. 37, 243-252] it has been shown how such data can be analysed by generating an (n x n) correlation matrix, rho, by correlating n full Powder Diffraction patterns, point by point. The rho matrix is used as a source of dendrograms and metric multidimensional plots in three or more dimensions which classify the patterns into sets related by similarity. In this paper, it is shown how Raman spectroscopy data can be used by themselves or as an adjunct to Powder Diffraction data by combining the two techniques using the individual differences scaling method (INDSCAL) of Carroll & Chang [Psychometria, (1970), 35, 283-319]. The method is very robust, and can be extended to other forms of spectroscopy. It is available as an option in the commercial PolySNAP3 computer program.

  • high throughput Powder Diffraction i a new approach to qualitative and quantitative Powder Diffraction pattern analysis using full pattern profiles
    Journal of Applied Crystallography, 2004
    Co-Authors: Christopher J Gilmore, Gordon Barr, Jonathan Paisley
    Abstract:

    A new integrated approach to full Powder Diffraction pattern analysis is described. This new approach incorporates wavelet-based data pre-processing, non-parametric statistical tests for full-pattern matching, and singular value decomposition to extract quantitative phase information from mixtures. Every measured data point is used in both qualitative and quantitative analyses. The success of this new integrated approach is demonstrated through examples using several test data sets. The methods are incorporated within the commercial software program SNAP-1D, and can be extended to high-throughput Powder Diffraction experiments.

Gordon Barr - One of the best experts on this subject based on the ideXlab platform.

  • High-throughput Powder Diffraction V: the use of Raman spectroscopy with and without X-ray Powder Diffraction data
    Journal of Applied Crystallography, 2009
    Co-Authors: Gordon Barr, Christopher J Gilmore, Gordon Cunningham, Wei Dong, Takashi Kojima
    Abstract:

    In high-throughput crystallography it is possible to accumulate large numbers of Powder Diffraction patterns on a series of related compounds, often polymorphs, salts or co-crystals. In previous papers [Gilmore, Barr & Paisley (2004). J. Appl. Cryst. 37, 231-242; Barr, Dong & Gilmore (2004). J. Appl. Cryst. 37, 243-252] it has been shown how such data can be analysed by generating an (n x n) correlation matrix, rho, by correlating n full Powder Diffraction patterns, point by point. The rho matrix is used as a source of dendrograms and metric multidimensional plots in three or more dimensions which classify the patterns into sets related by similarity. In this paper, it is shown how Raman spectroscopy data can be used by themselves or as an adjunct to Powder Diffraction data by combining the two techniques using the individual differences scaling method (INDSCAL) of Carroll & Chang [Psychometria, (1970), 35, 283-319]. The method is very robust, and can be extended to other forms of spectroscopy. It is available as an option in the commercial PolySNAP3 computer program.

  • high throughput Powder Diffraction i a new approach to qualitative and quantitative Powder Diffraction pattern analysis using full pattern profiles
    Journal of Applied Crystallography, 2004
    Co-Authors: Christopher J Gilmore, Gordon Barr, Jonathan Paisley
    Abstract:

    A new integrated approach to full Powder Diffraction pattern analysis is described. This new approach incorporates wavelet-based data pre-processing, non-parametric statistical tests for full-pattern matching, and singular value decomposition to extract quantitative phase information from mixtures. Every measured data point is used in both qualitative and quantitative analyses. The success of this new integrated approach is demonstrated through examples using several test data sets. The methods are incorporated within the commercial software program SNAP-1D, and can be extended to high-throughput Powder Diffraction experiments.

Jonathan Paisley - One of the best experts on this subject based on the ideXlab platform.

Jin-bei Zhang - One of the best experts on this subject based on the ideXlab platform.

  • A novel search/match system for X-ray Powder Diffraction data
    Chemometrics and Intelligent Laboratory Systems, 1993
    Co-Authors: Xiang-jun Lu, Wei-fan Zheng, Jin-bei Zhang
    Abstract:

    Abstract Lin, S.-F., Lu, X.-J., Zheng, W.-F. and Zhang, J.-B., 1993. A novel search/match system for X-ray Powder Diffraction data. Chemometrics and Intelligent Laboratory Systems , 20: 85–91. In this article, a new method for identifying components in crystalline mixtures by X-ray Powder Diffraction is presented. It is based on the Powder Diffraction file (PDF) provided by the JCPDS-International Centre for Diffraction Data and implemented on IBM PCs using MS FORTRAN 5.0. Unlike other methods, this method uses the weight factor for each Diffraction peak as a criterium, and can not only give a list of possible phases but also the definite components of the unknown sample by a simulation process. Actual samples including organic samples have been tested with high performance.