In this study, we fully employed the width of 0.8 eV for theoretical spectra, for simple comparison of spectral features and with experimental results, especially for Yb silicates. O K-edge spectra's dependence on the polymorph has been reported for cubic and monoclinic phases of Gd 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 , and Yb 2 O 3 . These results consistently indicate that spacing between peaks A and B (∆E) of the monoclinic phase is narrower than that of the cubic phase; specifically, the narrowing rates are approximately 90% for Gd 2 O 3 and 75-80% for the rest . This trend seems to reflect the changes in coordination environments (crystal fields) of lanthanide ions. . The energetic difference between the two phases (and the narrowing rate of the monoclinic to cubic phases) is coincident between theoretical and experimental results. Meanwhile, the O K-edge spectrum of hexagonal Yb 2 O 3 also has a smaller ∆E compared to that of the cubic case.