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Title: Tailored multivariate analysis for modulated enhanced diffraction

Modulated enhanced diffraction (MED) is a technique allowing the dynamic structural characterization of crystalline materials subjected to an external stimulus, which is particularly suited forin situandoperandostructural investigations at synchrotron sources. Contributions from the (active) part of the crystal system that varies synchronously with the stimulus can be extracted by an offline analysis, which can only be applied in the case of periodic stimuli and linear system responses. In this paper a new decomposition approach based on multivariate analysis is proposed. The standard principal component analysis (PCA) is adapted to treat MED data: specific figures of merit based on their scores and loadings are found, and the directions of the principal components obtained by PCA are modified to maximize such figures of merit. As a result, a general method to decompose MED data, called optimum constrained components rotation (OCCR), is developed, which produces very precise results on simulated data, even in the case of nonperiodic stimuli and/or nonlinear responses. Furthermore, the multivariate analysis approach is able to supply in one shot both the diffraction pattern related to the active atoms (through the OCCR loadings) and the time dependence of the system response (through the OCCR scores). Furthermore, when applied to realmore » data, OCCR was able to supply only the latter information, as the former was hindered by changes in abundances of different crystal phases, which occurred besides structural variations in the specific case considered. In order to develop a decomposition procedure able to cope with this combined effect represents the next challenge in MED analysis.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. National Research Council (CNR), Genova (Italy). Inst. of Crystallography
  2. Dept. of Electrical and Information Engineering, Bari (Italy)
  3. National Research Council (CNR), Genova (Italy). Inst. for Calculus Applications "Mauro Picone", Bari (Italy)
  4. Brookhaven National Lab. (BNL), Upton, NY (United States). Photon Science Division
  5. Brookhaven National Lab. (BNL), Upton, NY (United States). Chemistry Dept.
Publication Date:
Report Number(s):
BNL-111781-2016-JA
Journal ID: ISSN 1600-5767; JACGAR; R&D Project: CO009; KC0302010
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Journal of Applied Crystallography (Online)
Additional Journal Information:
Journal Name: Journal of Applied Crystallography (Online); Journal Volume: 48; Journal Issue: 6; Journal ID: ISSN 1600-5767
Publisher:
International Union of Crystallography
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; multivariate analysis; x-ray powder diffraction; modulated enhanced diffraction
OSTI Identifier:
1335384