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

International Tables for Crystallography (2006). Vol. C, ch. 5.2, p. 497

## Table 5.2.7.1

W. Parrish,a A. J. C. Wilsonb and J. I. Langfordc

aIBM Almaden Research Center, San Jose, CA, USA,bSt John's College, Cambridge CB2 1TP, England, and cSchool of Physics & Astronomy, University of Birmingham, Birmingham B15 2TT, England

 Table 5.2.7.1| top | pdf | Centroid displacement and variance W of certain aberrations of an energy-dispersive diffractometer [mainly from Wilson (1973), where more detailed results are given for the aberrations marked with an asterisk]
 The Soller slits are taken to be in the original orientation (Soller, 1924). For the notation, see the footnote.
 Aberration W Specimen displacement Included in equatorial divergence Specimen transparency* ? Equatorial divergence* for narrow Soller slits Axial divergence Refraction* Probably negligible at the present stage of technique Response variations Centroid ? Peak ? Interaction of Lorentz etc. factors and geometrical aberrations

Notation: A and B are the angular apertures (possibly equal) of the two sets of Soller slits; E is the energy of the detected photon; f (E) is the variation of a response (energy of the continuous radiation, absorption in the specimen etc.) with E; g(θ) is an angle-dependent response (Lorentz factor etc.); I(EE1) dE is the counting rate recorded at E when the energy of the incident photons is actually E1; R is the diffractometer radius; V is the variance and μ3 is the third central moment of the energy-resolution function I; 2X, 2Y, 2Z are the effective dimensions (possibly equal) of the source, specimen, and detector; the primes indicate differentiation; the averages <(Δθ)2> etc. are over the range of Bragg angles permitted by the slits etc.