IMAGING THE ELECTRON-DENSITY IN THE HIGHEST OCCUPIED MOLECULAR-ORBITAL OF GLYCINE

The spherically averaged electron density distribution of the highest occupied molecular orbital (HOMO) for the amino acid glycine has been determined by multichannel electron momentum spectroscopy. Comparison of the measured HOMO electron momentum distribution with near-Hartree-Fock limit and density functional theory (DFT) calculations for the Boltzmann-weighted sum of the eight predicted stable conformers indicates that electron correlation effects must be included in order to adequately reproduce the experimental results for glycine. The best-fitting DFT calculation determined with the Becke-Perdew gradient-corrected exchange-correlation functional was used to generate HOMO electron density maps for oriented glycine conformers. The result is shown for the most stable conformer.