A test of the accuracy of high-pressure measurements using a Merrill-Bassett diamond-anvil cell

The accuracy of structural parameters obtainable from measurements carried out with a Merrill-Bassett diamond-anvil high-pressure cell has been tested in an X-ray diffraction study of cubic CaF₂. The measurements were performed at 0.0001, 0.70, 1.70, 2.60, 2.90, 3.66 and 4.42 GPa. It was found that a simple modification of the shape of the gasket can eliminate the problem of partly obscured reflections and yield reliable values for the Ca and F thermal parameters - the only variables in this simple structure, and hence particularly sensitive to any systematic errors in the data.