The sub-bandgap energy loss satellites in the RIXS spectra of beryllium compounds

► Be 1s RIXS spectra have been measured in Be containing crystals phenakite and chrysoberyl. ► A strong energy loss sideband to the elastic scattering peak similar to BeO is found in both minerals. ► Additionally the Si 2p RIXS spectra of phenakite also show a strong energy loss sideband to the elastic scattering peak. ► The energy loss shoulder appears to result from lattice relaxation in the absorption site.