Impact of tetragonal rings on the stability of small fullerenes encapsulated with noble gas: A density functional theory survey

► A D4d isomer with two squares is proved as the most suitable host cage of noble gas. ► The 4/6/6/6/6 segment plays a key role on the outstanding stabilities of complexes. ► Thermodynamic property of endohedral compounds changes with different inserted atoms. ► There is hardly any electron transfer between inner atoms and fullerenes.