The effect of diffraction by the diamonds of a diamond-anvil cell on single-crystal sample intensities

The integrated intensities measured in X-ray single-crystal high-pressure structural studies using a diamond-anvil cell are shown to be reduced substantially when the diamonds diffract at the same setting as the sample - by as much as 50% in some cases. The pressure and wavelength dependence of this process have been studied and also the effect of changing the beam divergence by the use of a synchrotron beam. The consequences for the accuracy of structural information derived from data sets collected at high pressure are considered and a data-collection strategy for detecting and avoiding the effects of diamond diffraction is proposed.