An x-ray diffraction study of nanometer-sized amorphous silica particles was carried out at pressures of up to 7.4 GPa by using an energy dispersive synchrotron-radiation technique. We found that silica nanoparticles exhibit pressure-induced structural changes, which eventually lead to a permanent densification, at much lower pressures than what occurs in a bulk silica glass. Decreasing the size hence provides a new window for amorphous-amorphous transformations and also implies the appearance of a first-order-like, or thermodynamically controlled, transition pathway, even at room temperature.

• Received 12 March 2008

DOI:https://doi.org/10.1103/PhysRevB.77.132201