The electronic structure and surface chemistry of glycine adsorbed on Cu(110)

We present a combined density functional theory and x-ray emission spectroscopy study of the bonding and chemistry of glycine (NH2CH2COOH) chemisorbed on Cu(110). The amino acid deprotonates upon adsorption. The adsorbate exhibits a rich surface chemistry leading to several intermediate adsorption structures. The most stable geometry is found to involve both the carboxylic and amino functional end groups in the bond. This structure appears only after annealing to 400 K, which in the present work is attributed to a removal of surface or subsurface hydrogen from the metal. Comparison with experimental x-ray emission and near edge x-ray absorption fine structure (NEXAFS) spectra provide a detailed picture of the electronic structure for the most stable structure. This allows conclusions to be drawn regarding the covalent interaction of the adsorbate system. When combined with theoretical calculations addressing, e.g., the electrostatic adsorbate-substrate interaction, a complete picture of the surface chemical bond is obtained. (C) 2000 American Institute of Physics. [S0021-9606(00)70209-1].