Theoretical calculations and EELS measurements are performed for the investigation. The calculated lattice parameters of the bulks are almost the same as that of a previous study . In these structures, rigid SiO cases. Here, the peak A's intensity is significantly smaller than that of peak B, and the interpeak spacings (∆E) are narrower than those of Yb 2 O 3 (Table ). Due to these tendencies, peak A is ambiguously identified in the experimental spectra, especially for the Yb 2 Si 2 O 7 case (lower panel of Fig. ). Nevertheless, we can confirm the consistent behaviors between the calculated and experimental spectra, from the viewpoints of the smaller intensity and We should note that in this study, we applied the Yb 3+ PAW potential with 4f orbitals frozen as core orbitals. This derives a result of missing related peaks to the 4f orbitals. In The core-level spectra from 3d and 4d electrons (M 4,5 and N 4,5 -edges) of an R element may be applied for identification of rare-earth compounds. Generally, these edges are useful for specifying R species and valence states . However, recent two papers that reported the Gd N 4,5 -edge spectra of monoclinic and cubic Gd 2 O 3 and Yb N 4,5 -edge spectra of Yb 2 SiO 5 and Yb 2 Si 2 O 7 provided indistinguishable results for each. Furthermore, in these cases, the transition involves multiplet coupling and 4f orbitals . Moreover, the calculation scheme adopted in this study is difficult to apply, at least regarding the PAW potential applied for Yb atoms. Meanwhile, as a systematic behavior exists on the O K-edge spectra over rare-earth elements in Ln 2 O 3 , the acquired knowledge on O K-edge spectra in this study is transferable to other rare-earth oxides and silicates more or less.