Electronic Structures of CaSiO3 Glass under Megabar Pressures: Ca L2,3-Edge and O K-Edge X-ray Raman Scattering

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.