Commission on Crystallographic Nomenclature

Statistical descriptors in crystallography

1989 report - authors and abstract

Acta Cryst. (1989). A45, 63-75[pdf icon]

Statistical Descriptors in Crystallography - Report of the International Union of Crystallography Subcommittee on Statistical Descriptors*

  • D. Schwarzenbach (Chairman), Institut de Cristallographie, University of Lausanne, BSP Dorigny, CH-1015 Lausanne, Switzerland
  • S. C. Abrahams (ex officio, IUCr Commission on Crystallographic Nomenclature), AT&T Bell Laboratories, 600 Mountain Ave., Murray Hill, NJ 07974, USA
  • H. D. Flack, Laboratoire de Cristallographie aux Rayons X, University of Geneva, 24 quai Ernest Ansermet, CH-1211 Genève 4, Switzerland
  • W. Gonschorek, Institut für Physikalische Chemie der TH Darmstadt, Aussenstelle in KFA/ZFR, Postfach 913, D-5170 Jülich, Germany
  • Th. Hahn (ex officio, IUCr Commission on Crystallographic Nomenclature), Institut für Kristallographie, RWTH, Templergraben 55, D-5100 Aachen, Germany
  • K. Huml (ex officio, IUCr Commission on Crystallographic Computing), Laboratory of X-ray Polymer Structure Analysis, Institute of Macromolecular Chemistry, Czech Academy of Science, 162 06 Praha 6, CSSR
  • R. E. Marsh, Chemistry Department, California Institute of Technology, Pasadena, CA 91125, USA
  • E. Prince, National Bureau of Standards, Reactor Radiation Division, Gaithersburg, MD 20899, USA
  • B. E. Robertson, Department of Physics and Astronomy, University of Regina, Regina, Sask. S4S 0A2, Canada
  • J. S. Rollett, Oxford University Computing Laboratory, 8 - 11 Keble Road, Oxford OX1 3QD, England and
  • A. J. C. Wilson (ex officio, IUCr Commission on Crystallographic Nomenclature), University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, England.
(Received 28 March 1988; accepted 2 September 1988)

The Subcommittee has attempted to elucidate the nature of problems encountered in the definition and use of statistical descriptors as applied to crystallography and to propose procedural improvements. The report contains

  • a dictionary of statistical terms established for use by experimentalists
  • a description of the statistical basis of refinement procedures
  • sections dealing with defects in the physical model used for refinement, and with the choice and significance of weighting schemes; and
  • recommendations, some of which may be readily implemented, whilst others may require a long-term effort to bring them into general use.


It is a pleasure to thank our colleagues associated with the IUCr and particularly Dr D.J. Finney of the International Statistics Institute for clarifying comments on an earlier draft.
* Appointed 27 Februrary 1985 as a Subcommittee of the IUCr Commission on Crystallographic Nomenclature. Following a review by the Chairman of all relevant IUCr Commissions, the Final Report was accepted on 9 May 1988 by the Commission and on 2 September 1988 by the Executive Committee.
© 1989, 1995 International Union of Crystallography
Updated 18th Sept. 1996

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