Tables for
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C. ch. 5.5, pp. 541-551

Chapter 5.5. Neutron methods

B. T. M. Willisa

aChemical Crystallography Laboratory, University of Oxford, 9 Parks Road, Oxford OX1 3PD, England

Some comments are given on the derivation of lattice parameters from neutron powder patterns.

Keywords: diffractometers; high-resolution powder diffractometers; lattice-parameter determination; neutron diffraction; neutron powder diffractometers; powder-pattern indexing; Rietveld method.

In general, one would not expect to measure lattice parameters as precisely with neutrons as with X-rays. The main reason for this is the need to relax the resolution of the diffraction peaks observed in neutron diffraction, in order to obtain reasonable count rates. However, the high-resolution powder diffractometer D2B (on the reactor source at the Institut Laue–Langevin) and the high-resolution powder instrument HRPD (on the pulsed source at the Rutherford Appleton Laboratory) have resolutions approaching that of X-ray diffractometers. Using Rietveld refinement, lattice parameters can be determined to a precision of a few parts in 104 (Fischer et al., 1986[link]).

Neutron methods are better suited to the indexing of the powder pattern. This requires the accurate measurement of the d spacings of the lowest-index lines in the pattern. Whereas d spacings measured with X-rays at low values of (sin θ)/λ tend to have systematic errors, this is not such a serious problem with neutrons. It is relatively straightforward, using the time-of-flight pulsed-neutron method, to measure the d spacings of the first 20–30 lines of a powder pattern to better than 0.1%.


First citationFischer, P., Zolliker, P., Meier, B. H., Ernst, R. R., Hewat, A. W., Jorgensen, J. D. & Rotella, F. J. (1986). Structure and dynamics of terephthalic acid from 2 to 300 K. J. Solid State Chem. 61, 109–125.Google Scholar

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