X-ray diffraction study of dysprosium single crystal samples in a Diamond Anvil Cell (DAC).

摘要

X-ray diffraction is the basis of crystallography, the study of the structure of crystals. It uses X-rays of a wavelength on the order of the size of atoms, so it can resolve the positions of individual atoms in a crystal. Illuminating the crystal with a well-collimated X-ray beam produces X-rays diffracted in a certain direction for a specific crystal orientation. By analyzing the relative phase of the incoming and outgoing scattered X-rays, the unique arrangements of atoms can be determined and the structure of the crystal can be solved.;There is a long standing controversy regarding the crystal structures and densities of high pressure (HP) phases of rear-earth metals. Over the last couple of decades the dysprosium (Dy) structure has been obtained by polycrystalline diffraction from samples in the DACs (Diamond Anvil Cells). Due to HP powder diffraction issues of deviatoric stress and pressure gradient, the structures found are controversial. These experimental controversies have as a present consequence lack of accurate lanthanides phase diagram.;In the experimental work conducted for this thesis, dysprosium was studied using high pressure single crystal X-ray diffraction method. Single crystals of Dy were flux grown. The experiment was conducted at Advanced Photon Source (APS) synchrotron radiation beam line at Argonne National Lab (ANL). The experimental results reported were for the twinned crystal symmetry indexed in 0.7-3.8 GPa pressure region.