“…The vacancies at fourth-and fifth-nearest-neighbors along the [1 0 0] and [2 1 0] directions also have little influence on cubic symmetry of Sm 2+ . Sites C and D with C 3v symmetries are presumably attributed to the Sm 2+ ions associated with other defects, such as interstitial fluorine atoms [13]. The fluorescence properties of sites C and D will be discussed in detail elsewhere.…”