Application of energy-resolved measurements to laue diffraction

Determination of unit-cell parameters, deconvolution of harmonics and assignment of systematic absences

Quentin S. Hanley, John W. Campbell, M Bonner Denton

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The use of energy-resolved area detection of Laue diffraction patterns for the determination of unit-cell parameters and systematic absences is demonstrated. Seven different crystals having previously known unit cells were re-examined using Laue diffraction methods. These crystals included four different crystal systems including cubic, orthorhombic, tetragonal and monoclinic cells. The crystals had cell sizes ranging from 179.4 to 4588.3 Å3. Comparison of known and re-determined cells showed good agreement (ratio of known to measured cells = 0.987 ± 0.18). A single procedure was suitable for all unit-cell determinations. The accuracy of the method is presently limited by the quality of the available energy measurements. Some of the crystals represent space groups containing systematic absences normally obscured by harmonic overlap when using the Laue method. These include absences due to 21 screw axes (h, k or l = 2n + 1) and cell centering (h + k = 2n + 1). All systematic absences were identified using a combination of multiple linear regression with either stepwise elimination or stepwise inclusion and an F test for assignment of systematic absence. The methods are discussed in detail and simulations are used to evaluate critical tolerances for future systems.

Original languageEnglish (US)
Pages (from-to)214-222
Number of pages9
JournalJournal of Synchrotron Radiation
Volume4
Issue number4
StatePublished - Jul 1 1997

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Electric power measurement
Deconvolution
Diffraction
harmonics
Crystals
cells
diffraction
energy
crystals
Laue method
Linear regression
Diffraction patterns
screws
regression analysis
elimination
diffraction patterns
inclusions

Keywords

  • Energy-resolved measurements
  • Foil-mask spectrometers
  • Harmonic deconvolution
  • Laue diffraction
  • Screw axes
  • Systematic absences
  • Unit-cell determination

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)
  • Instrumentation
  • Atomic and Molecular Physics, and Optics
  • Radiation

Cite this

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title = "Application of energy-resolved measurements to laue diffraction: Determination of unit-cell parameters, deconvolution of harmonics and assignment of systematic absences",
abstract = "The use of energy-resolved area detection of Laue diffraction patterns for the determination of unit-cell parameters and systematic absences is demonstrated. Seven different crystals having previously known unit cells were re-examined using Laue diffraction methods. These crystals included four different crystal systems including cubic, orthorhombic, tetragonal and monoclinic cells. The crystals had cell sizes ranging from 179.4 to 4588.3 {\AA}3. Comparison of known and re-determined cells showed good agreement (ratio of known to measured cells = 0.987 ± 0.18). A single procedure was suitable for all unit-cell determinations. The accuracy of the method is presently limited by the quality of the available energy measurements. Some of the crystals represent space groups containing systematic absences normally obscured by harmonic overlap when using the Laue method. These include absences due to 21 screw axes (h, k or l = 2n + 1) and cell centering (h + k = 2n + 1). All systematic absences were identified using a combination of multiple linear regression with either stepwise elimination or stepwise inclusion and an F test for assignment of systematic absence. The methods are discussed in detail and simulations are used to evaluate critical tolerances for future systems.",
keywords = "Energy-resolved measurements, Foil-mask spectrometers, Harmonic deconvolution, Laue diffraction, Screw axes, Systematic absences, Unit-cell determination",
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TY - JOUR

T1 - Application of energy-resolved measurements to laue diffraction

T2 - Determination of unit-cell parameters, deconvolution of harmonics and assignment of systematic absences

AU - Hanley, Quentin S.

AU - Campbell, John W.

AU - Denton, M Bonner

PY - 1997/7/1

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N2 - The use of energy-resolved area detection of Laue diffraction patterns for the determination of unit-cell parameters and systematic absences is demonstrated. Seven different crystals having previously known unit cells were re-examined using Laue diffraction methods. These crystals included four different crystal systems including cubic, orthorhombic, tetragonal and monoclinic cells. The crystals had cell sizes ranging from 179.4 to 4588.3 Å3. Comparison of known and re-determined cells showed good agreement (ratio of known to measured cells = 0.987 ± 0.18). A single procedure was suitable for all unit-cell determinations. The accuracy of the method is presently limited by the quality of the available energy measurements. Some of the crystals represent space groups containing systematic absences normally obscured by harmonic overlap when using the Laue method. These include absences due to 21 screw axes (h, k or l = 2n + 1) and cell centering (h + k = 2n + 1). All systematic absences were identified using a combination of multiple linear regression with either stepwise elimination or stepwise inclusion and an F test for assignment of systematic absence. The methods are discussed in detail and simulations are used to evaluate critical tolerances for future systems.

AB - The use of energy-resolved area detection of Laue diffraction patterns for the determination of unit-cell parameters and systematic absences is demonstrated. Seven different crystals having previously known unit cells were re-examined using Laue diffraction methods. These crystals included four different crystal systems including cubic, orthorhombic, tetragonal and monoclinic cells. The crystals had cell sizes ranging from 179.4 to 4588.3 Å3. Comparison of known and re-determined cells showed good agreement (ratio of known to measured cells = 0.987 ± 0.18). A single procedure was suitable for all unit-cell determinations. The accuracy of the method is presently limited by the quality of the available energy measurements. Some of the crystals represent space groups containing systematic absences normally obscured by harmonic overlap when using the Laue method. These include absences due to 21 screw axes (h, k or l = 2n + 1) and cell centering (h + k = 2n + 1). All systematic absences were identified using a combination of multiple linear regression with either stepwise elimination or stepwise inclusion and an F test for assignment of systematic absence. The methods are discussed in detail and simulations are used to evaluate critical tolerances for future systems.

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KW - Foil-mask spectrometers

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KW - Laue diffraction

KW - Screw axes

KW - Systematic absences

KW - Unit-cell determination

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