  Several dissociated and two non-dissociated adsorption structures of the
phenol molecule on the Si(001)-(2 \times 1) surface are studied using density
functional theory with various exchange and correlation functionals. The
relaxed structures and adsorption energies are obtained and it is found that
the dissociated structures are energetically more favourable than the
non-dissociated structures. However, the ground state energies alone do not
determine which structure is obtained experimentally. To elucidate the
situation core level shift spectra for Si 2p and C 1s states are simulated and
compared with experimentally measured spectra. Several transition barriers were
calculated in order to determine which adsorption structures are kinetically
accessible. Based on these results we conclude that the molecule undergoes the
dissociation of two hydrogen atoms on adsorption.
