LORENTZ FACTOR IN DIFFRACTION BY MATERIALS WITH A (ONE-DIMENSIONAL CRYSTAL PLUS 2-DIMENSIONAL POWDER) STRUCTURE

The Lorentz factor in diffraction by materials having the morphology of a one-dimensional crystal in one-direction and a two-dimensional powder in the other directions, such as highly oriented pyrolytic graphite, is shown to be the same as that by a conventional 3-dimensional single crystal, in spite of the powder nature of the material. This is true for all the sample orientations commonly employed in the diffractometer method with one exception: when the crystalline axis of the sample is aligned parallel to the incoming beam, the Lorentz factor is given by (1/sin(2)2theta).