Adsorption of C60 on Au(111) revisited: A van der Waals density functional study

We address the dispersion force in a C-60/Au(111) interface using the van der Waals density functional with improved exchange [V. R. Cooper, Phys. Rev. B 81, 161104(R) (2010)] and nonlocal correlation [K. Lee, E. D. Murray, L. Kong, B. I. Lundqvist, and D. C. Langreth, Phys. Rev. B 82, 081101(R) (2010)]. We found that the adsorption is solely attributed to the nonlocal correlation, i.e., the van der Waals (vdW) forces, and the correct account of vdW attraction between C-60 molecules is also essential to obtain accurate binding energy. The bonding of C-60 is, however, covalent-like, which is originated from the hybridization of the lowest unoccupied molecular orbital of C-60, in agreement with a previous theoretical study.