Abstract:
The adsorption of benzene molecules onto the Cu(110) surface has been studied using
a crystalline linear combination of atomic orbitals approximation (LCAO).
Adsorption energetics have been modeled at both the Hartree-Fock (HF) and density
functional theory (DFT) level, and scanning tunneling microscope (STM) images
generated for the preferred adsorption geometry. The calculated binding energies are
strongly dependent upon basis set superposition errors (BSSE). As expected HF
provides a relatively poor description of this loosely bound system, and is found to be
unbound when BSSE is taken into account. Inclusion of electron correlation through
DFT methods gives an optimized binding energy of 106 kJ mol-1 with the benzene
molecule occupying a bridging site between the rows of surface copper atoms and an
adsorption height of approximately 2 Å. This figure takes account of relaxation of
benzene upon absorption with the hydrogen atoms tilting away from the surface. Our
predicted energetics compare favourably with previous theoretical studies using
cluster methods and experimental binding energies determined from temperature
programmed desorption (TPD). We have also simulated scanning tunneling
microscope (STM) images using the Tersoff and Hamann method and compare our
results with recent experimental measurements. Our simulation suggests the
experimental image results from a benzene dimer rather than an isolated molecule.
