Structural stability and electronic property of C68X4 (X = H, F, and Cl) fullerene compounds

A systematic study on the geometrical structures and electronic properties of C68X4 (X = H, F, and Cl) fullerene compounds has been carried out on the basis of density functional theory. In all classical C68X4 isomers with two adjacent pentagons and one quasifullerene isomer [Cs:C68(f)] containing a heptagon in the framework, the Cs:0064 isomers are most favorable in energy. The addition reaction energies of C68X4 (Cs:0064) are high exothermic, and C68F4 is more thermodynamically accessible. The C68X4 (Cs:0064) possess strong aromatic character, with nucleus independent chemical shifts ranging from −22.0 to −26.1 ppm. Further investigations on electronic properties indicate that C68F4 and C68Cl4 could be excellent electron-acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities (3.29 and 3.15 eV, respectively). The Mulliken charge populations and partial density of states are also calculated, which show that decorating C68 fullerene with various X atoms will cause remarkably different charge distributions in C68X4 (Cs:0064) and affect their electronic properties distinctly. Finally, the infrared spectra of the most stable C68X4 (Cs:0064) molecules are simulated to assist further experimental characterization.