under shock compression*

SiO₂ and TiO₂ are known to undergo phase transitions under shock compression. The nature of these transitions and the resulting high-pressure phases are of fundamental interest for understanding the dynamic response of minerals, for characterizing natural impact sites, and for understanding high-pressure phases of planetary interiors. In this study, in situ x-ray diffraction experiments on shock-compressed SiO₂ and TiO₂ were conducted at the Dynamic Compression Sector of the Advanced Photon Source. The lattice-level structure was investigated through time-resolved x-ray diffraction measurements on samples reaching a peak stress ranging from 12 to 70 GPa. For SiO₂, we have examined natural low-porosity polycrystals as well as fused silica. For TiO₂, we have studied single crystals in different orientations. Our results provide direct constraints on the nature of the high-pressure phases formed under shock compression in these materials.