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International
Tables for Crystallography Volume G Definition and exchange of crystallographic data Edited by S. R. Hall and B. McMahon © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. G. ch. 3.3, pp. 127-128
Section 3.3.8.8. Noting sample orientation
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NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8562, USA |
For texture measurements, intensity measurements can be made as a function of different sample setting angles. These setting angles can be specified using _pd_meas_angle_chi, _pd_meas_angle_omega and _pd_meas_angle_phi. The change in these values may be specified by including these data items in the loop with the diffraction intensities. In some cases, it may be more convenient to separate measurements with different setting angles into different blocks. In this case, the values for the setting angle(s) that are invariant will be set outside of a loop.
It is common in powder diffraction to reduce preferred orientation and improve crystallite averaging by rocking or rotating the sample. This is indicated by specifying the axis used for rocking, usually ![[\varphi]](/teximages/acpre6/acpre6fi68.svg)
for capillary specimens or ![[\chi]](/teximages/bach4o4/bach4o4fi266.svg)
for flat-plate specimens, as _pd_meas_rocking_axis. The data item _pd_meas_rocking_angle is used to record the angular range through which the sample is rocked, where 360 indicates that one complete revolution occurs during each counting period. Numbers greater than 360 are possible.
