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

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