Nonlocal-density-functional bond-energy calculations of cage-shaped carbon fullerenes: C32 and C60.

Abstract

The bond energies of ${\mathrm{C}}_{32}$ and ${\mathrm{C}}_{60}$ fullerenes have been calculated by a self-consistent molecular-orbital method based on nonlocal-density-functional theory with the generalized gradient approximation (GGA). These results were compared with those obtained with use of the local-density approximation (LDA). The bond energies calculated with the GGA (${\mathrm{C}}_{60}$, 7.24 eV/atom; ${\mathrm{C}}_{32}$, 6.88 eV/atom) were about 1.3 eV/atom (15%) smaller than those calculated with the LDA, and the GGA result for ${\mathrm{C}}_{60}$ was found to be in good agreement with the evaluated value from the experimental formation energy. The differences in bond lengths, force constants, and orbital energies for the same molecular structure ---except for the core orbitals---between the LDA and GGA were small, compared with the difference in bond energies.