International
Tables for
Crystallography
Volume H
Powder diffraction
Edited by C. J. Gilmore, J. A. Kaduk and H. Schenk

International Tables for Crystallography (2018). Vol. H, ch. 1.1, p. 8

Figure 1.1.11 

R. E. Dinnebiera* and S. J. L. Billingeb,c

aMax-Planck-Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany,bDepartment of Applied Physics and Applied Mathematics, Columbia University, 500 West 120th Street, Room 200 Mudd, MC 4701, New York, NY 10027, USA, and cCondensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, PO Box 5000, Upton, NY 11973–5000, USA
Correspondence e-mail:  r.dinnebier@fkf.mpg.de

[Figure 1.1.11]
Figure 1.1.11

Simplified representation of the Ewald-sphere construction as a circle in two dimensions. Illustration of the region of reciprocal space that is accessible in a powder diffraction experiment. The smaller circle represents the Ewald sphere. As shown in Fig. 1.1.10[link], a powder sample has crystallites in all possible orientations, which is modelled by rotating the reciprocal lattice to sample all orientations. An equivalent operation is to rotate the Ewald sphere in all possible orientations around the origin of reciprocal space. The volume swept out is the region of reciprocal space accessible in the experiment. [Reproduced from Dinnebier & Billinge (2008[link]) with permission from the Royal Society of Chemistry.]