Department of Chemical Engineering, Minghsin University of Science and Technology^* Institute of Chemistry, Academia Sinica, Taiwan^** Department of Chemistry, Beijing Normal University, Beijing^***
○Chi-Rung Lee^* Chin-Yu Chen^** De-Cai Fang^*** Ting-Hua Tang^***

H-H interaction is shown in the quantum theory of atoms in molecules. The molecular electron densities are obtained both from X-ray diffraction data at low temperature and from a periodic density functional theory calculation. Intra and intermolecular interactions of biphenyl is investigated in terms of topological analyses. The features of the deformation densities, Laplacian distributions, bond paths, and atomic domains are shown to describe the variety bonding. All the interactions are verified by the location of the bond critical point and its associated topological properties. From the experimental multipole model and theoretical results, di-hydrogen bonds can be verified by molecular graph, and the related interactions energies could be discussed by calculations.