Electronic Structures of CaSiO3 Glass under Megabar Pressures: Ca L 2,3-Edge and O K -Edge X-ray Raman Scattering

Abstract The extreme densification of silicate glasses above 100 GPa reorganizes chemical bonding around both the oxygen network and the network-modifying cations. These responses, however, have largely been probed separately, leaving their coupling during extreme densification unresolved. Here, we report the first O K-edge and Ca L2,3-edge X-ray Raman scattering measurements of CaSiO3 glass up to 120 GPa, providing element-specific access to the electronic structures under extreme compression. Enhanced oxygen proximity near 100 GPa raises the oxygen electronic states, whereas gradual Ca–O compaction shifts the calcium electronic states to lower energy through increased ligand-field interaction. Pressure-driven structural diversity and network distortion enhance electronic dispersion, broadening the oxygen and calcium density of states at megabar pressures. Comparison with O K-edge results for SiO2 and MgSiO3 glasses reveals that the larger ionic radius of Ca2+ suppresses the pressure-induced shift in electronic states near 100 GPa, highlighting how cation size controls electronic structures to evolve during extreme glass densification. These findings have implications for the stability of Ca-rich melts in planetary interiors and the design of mechanically strengthened glasses.