For all six configurations, the adsorption and replacement energy values, interatomic distances between the Aloct atom and the coordinated O atom of 5-FU, as well as atoms participating in hydrogen bonds are listed in Table . Despite different 5-FU positions, coordination modes, and hydrogen bonding patterns, five out of six configurations are close in energy, falling within about 6 kJ mol -1 . Among them, the configurations indexed 1_O4 and 2_O2 have the lowest adsorption energies, and will therefore be in the focus of the following discussion.