Ultrafast structural dynamics of silicate glasses in extreme environments

Abstract

A fundamental understanding of network structure and associated atomic-scale mechanisms in silicate glasses under dynamic compression is crucial for explaining several phenomena including, planetary formation, core-mantle boundary dynamics, and the design of high-performance glasses for military and aerospace application. Although pure silica has been extensively studied, the behavior of modified silicate glasses is often extrapolated from pure silica, with direct structural evidence remaining limited. We directly probed nanosecond-scale structural dynamics in silicate glasses containing network-forming cations (borosilicate glass) and network-modifying cations (soda-lime glass) using time-resolved X-ray diffraction and laser-driven shock compression. Distinct polymorphic behavior, strongly dependent on the network structure, was observed between 40 and 65 GPa. Borosilicate glass undergoes polymorphic phase transitions with crystal symmetry strongly dependent on the pressure, whereas soda-lime glass exhibits changes in coordination number without a corresponding change in the global symmetry. Above 65 GPa, both glasses respond similarly, exhibiting increasing densification and structural disorder, ultimately leading to melting.