Molecular structure and piezoelectric properties of C₆₀

Density functional theory (DFT) was employed to investigate the elastic strength and electronic properties of C₆₀(Ih) in their ground electronic state. Most of the properties were examined for larger structure distortions. The over-all elastic constant were derived from the near-equilibrium potential energy curves (PECs) in five independent directions[according to symmetries by D_5d, D_3d, D_2h, C_2h(1), C_2h(2)]. By extension of the distortions as large as the molecular structure of C₆₀ were destroyed. The necessary energies were obtained, which quantitatively illuminated the stability of C₆₀ theoretically. Analytical polynomial fit of the full PECs reproduced the energy data accurately. It was found that the peak positions obtained from the computed electronic absorption spectra had a constant shift of about 0.4 eV in C₆₀ compared with the experiments. The calculated and corrected spectra of C₆₀ were in excellent agreement with the experiments. Particularly, elongations in the directions of D_5d and compression in D_2h encountered potential energy surface cross-linkages, which might be considered as a single electron pump for the piezoelectric application of C₆₀ in design of single electron devices.