Ab initio and density functional study on fullerene C44 and its derivatives

► The MP2/6-31G* and MP2/TZVP calculations show that D3h:72 C44 is the most stable structure. ► D2:75 and D2:89 C442− are predicted to be the two most stable isomers, and they are highly aromatic. ► The calculated AEAs of the D2:75 and D2:89 isomers are in good agreement with experimental data. ► Exohedral derivatives C44X14 formed from the initial D3h:72 C44 are molecules with high stability. ► D2:75 is suggested as the most probable isomer for the experimentally observed Ca@C44.