The Lorentz-Polarization Factor and Preferred Orientation in Oriented Clay Aggregates

R. C. Reynolds Jr.
Department of Earth Sciences, Dartmouth College Hanover, New Hampshire 03755

Abstract: A closed-form equation was derived that describes the powder-ring distribution factor as a function of 2θ, soller slit collimation, and σ*, which is defined as the standard deviation of an axially symmetrical Gaussian orientation function. Methods were developed for measuring σ* in the reflection mode by means of a θ/2θ diffractometer. Six experimental arrangements for a sedimentary chlorite showed widely different intensity ratios of the 001/005 reflections and gave a standard deviation of ±5.8% when corrected by the theory. The absolute integrated intensities of the 003 reflection from eleven illite samples provided an eight-fold maximum range which, when corrected, yielded a standard deviation of ±7.7%.

The intensity distributions within each of two X-ray powder diffraction patterns obtained from instruments with different soller-slit configurations could not be directly compared at low diffraction angles unless corrections, based on σ*, were introduced to allow for the differences in axial divergence.

Key Words: Chlorite • Illite • Intensity distribution • Lorentz factor • Orientation • Soller slits • X-ray powder diffraction

Clays and Clay Minerals; August 1986 v. 34; no. 4; p. 359-367; DOI: 10.1346/CCMN.1986.0340402
© 1986, The Clay Minerals Society
Clay Minerals Society (www.clays.org)