The structure of densified As2O3 glasses

In situ high energy X-ray diffraction and Raman experiments have been carried out to probe the structure changes of vitreous As2O3 under pressure. The first sharp diffraction peak reduces in intensity up to 10 GPa, indicating a breakdown of intermediate range order with pressure. All features in the Raman spectra broaden with increasing pressure up to 11.6 GPa. The mode at 378 cm−1 associated with As4O6 molecule-like vibrations increases in intensity up to 6.2 GPa and decreases at higher pressures. In addition, X-ray and neutron structure factors have been measured for normal density and permanently densified As2O3 glasses recovered from 10 and 23 GPa. The results show the local AsO3 pyramids and 3-membered rings essentially remain intact after compression. The increase in density is mainly associated with an inward shift of the third nearest neighbor peak in the X-ray radial distribution function, which indicates an increased packing of 3-membered AsO3 rings.