Analysis of high-energy x-ray diffraction data at high pressure: the case of vitreousAs2O3 at 32 GPa

Abstract

The x-ray structure factor of vitreousAs2O3 has been measured at 32 GPa in a laser-perforated diamond anvil cell using amonochromatic, micro-focused high-energy x-ray beam. The experimental correctionprocedures are discussed in detail, and they yield reliable data over the rangeQ = 0.3–13.5 Å−1. The use of modified form factors to analyse the scattering data is presented to account for chargetransfer. Analysis of the radial distribution function yields an increase in the coordination numberfrom 3.1 ± 0.3 oxygen atoms surrounding an arsenic atom at normal pressure to4.8 ± 0.5 at 32 GPa with only a slight change in the As–O bond length. Substantial structuralchanges are observed at higher distances, extending up to 18 Å in real space.