Structural and electronic properties of neutral and charged Ca8C12 metal carbides

► Low-lying structures for Ca8C12 and Ca8C12+ clusters prefer cage-like structures. ► A compact structure is prevailing for Ca8C12- cluster. ► The hollow cage-like structures are magnetic. ► The donation and back donation of valence electrons account for the CaC bonding. ► The net charge on Ca ion in the low-lying structures is around +1.4e.