High-pressure x-ray diffraction studies on the structure of liquid silicate using a Paris-Edinburgh type large volume press

An experimental setup for high-pressure liquid structure studies with synchrotron x-ray diffraction using the Paris-Edinburgh press has been installed at station 16-BM-B (HPCAT) of the Advanced Photon Source, Argonne National Laboratory. By collecting energy-dispersive data with a synchrotron white beam at various 2 theta angles, the present device allows us to obtain the structure factor, S(Q), over a wide range of Q ( = 4 pi sin theta/lambda) owing to the excellent angular accessibility up to 37 degrees in 2 theta and high energy photons well beyond 100 keV. We have successfully collected XRD data on silicate (albite, NaAlSi3O8) liquids with Q up to similar to 22 angstrom(-1) and pressure up to 5.3 GPa and temperature 1873 K, and obtained the radial distribution function, G(r), with a reasonable resolution. The T-O bond length (where T = Al, Si), which is a fundamental measure of local structure for aluminous silicate consisting of SiOn and AlOn, polyhedra (tetrahedra at 1 atm condition), was found to be slightly shortened to 1.626 angstrom compared to that of glass at 1 atm. The T-O-T bound angle, which is the linkage of the above polyhedra, is the most responsible for densification. The T-O-T peak in G(r) splits into two peaks, suggesting a differentiation of the bond angle at high-pressure. The present technical development demonstrates that the Paris-Edinburgh press is suitable for studies of silicate liquids under high-pressure conditions. (C) 2011 American Institute of Physics. [doi:10.1063/1.3514087]