查看文章

A high-resolution, low-temperature X-ray diffraction data set on dl-histidine, collected with a CCD detector, is used in the analysis of molecular bonding and intermolecular interactions. The molecular dipole moment in the crystal is enhanced relative to that from HF and DFT calculations. Topological properties of the molecular electron density differ from theory for the polar bonds but generally agree well for the C−C bonds in the molecule. A major aim of the study is the evaluation of the electrostatic contribution to the intermolecular interactions from the experimental density. The electrostatic interaction energies between pairs of neighboring molecules, as calculated from the experimental density, compare reasonably well with the total interaction energies from supermolecule calculations. The agreement is somewhat improved by the addition of nonelectrostatic repulsion and dispersive terms, which together …