Ab initio study of pentacene on the Fe(1Â 0Â 0) surface

The adsorption structure and the spin-resolved electronic properties of a pentacene molecule adsorbed on the Fe(1 0 0) surface are investigated by means of ab initio calculations on the basis of the density functional theory. The pentacene molecule was found to adsorb with its molecular plane lying flat on the surface at low coverage and with it tilting from the surface at high coverage. The spin polarization is negative at the donated molecular orbitals and positive at the backdonated (induced 4b1u(π∗)) orbital close to the Fermi level, which is indicated by the computation of the spin density distributions and plane-averaged density of states at the vacuum side. This opposite spin polarization is quite consistent with a previous experimental result of spin asymmetry in the spin-polarized metastable-atom deexcitation spectra.