Sc2S@C-80 has been detected but not been isolated and characterized. To investigate the structures and properties of Sc2S@C-80, a density functional theory study on fullerene C-80 and metallofullerene Sc2S@C-80 was carried out. The calculations demonstrate that Sc2S prefers to be encapsulated inside D-5h-C-80 and C-2v-C-80, instead of the well-known I-h-C-80. The two lowest-energy isomers of Sc2S@C-80 may coexist in the soot. The calculations reveal that there exists strong covalent interaction between the cage and Sc2S cluster, suggesting Sc2S@C-80 may have different properties from those usual C-80-based metallofullerenes. Raman spectra are provided to help future experimental identification of Sc2S@C-80. (C) 2014 Elsevier B.V. All rights reserved.