A mechanism of the adhesion between an aluminum oxide surface and an epoxy resin is investigated by using density functional theory (DFT) calculations. Force field simulations are carried out for a better understanding of the dynamic behavior of the resin on the surface and for constructing models for DFT calculations. Stable structures of a resinÀ surface complex, adhesion energies, and details about interaction sites are obtained from geometry optimizations for some models based on DFT calculations with a plane-wave basis set and periodic boundary conditions. DFT calculations reveal that hydroxyl groups of the epoxy resin interact with the surface of aluminum oxide to form hydrogen bonds, which work as a main force for the adhesion. Plots of energy versus vertical distance of the resin from the surface are nicely approximated by the Morse potential. The force required for detachment of the resin from the surface can be estimated from the maximum value of the forceÀdistance curve, which is obtained from the derivative of the potential energy curve. Obtained results demonstrate that hydrogen bonds play a central role for the adhesion between an aluminum oxide surface and an epoxy resin.

An empirical observation of a relationship between a striking feature of electronic transmission through a π-system, destructive quantum interference (QI), on one hand, and the stability of diradicals on the other, leads to the proof of a general theorem that relates the two. Subject to a number of simplifying assumptions, in a π-electron system, QI occurs when electrodes are attached to those positions of an N-carbon atom N-electron closed-shell hydrocarbon where the matrix elements of the Green's function vanish. These zeros come in two types, which are called easy and hard. Suppose an N+2 atom, N+2 electron hydrocarbon is formed by substituting 2 CH 2 groups at two atoms, where the electrodes were. Then, if a QI feature is associated with electrode attachment to the two atoms of the original N atom system, the resulting augmented N+2 molecule will be a diradical. If there is no QI feature, i.e., transmission of current is normal if electrodes are attached to the two atoms, the resulting hydrocarbon will not be a diradical but will have a classical closed-shell electronic structure. Moreover, where a diradical exists, the easy zero is associated with a nondisjoint diradical, and the hard zero is associated with a disjoint one. A related theorem is proven for deletion of two sites from a hydrocarbon. molecular conductance | diradicals | quantum interference | determinants | nonbonding orbitals C onnections between concepts that at first sight seem unrelated are always intriguing, and hint at an underlying cause. We came across one such correspondence recently, between the existence of π-diradicals, on one hand, and quantum interference (QI) in the transmission of electrons across a π-system on the other.

The symmetry of a molecule junction has been shown to play a significant role in determining the conductance of the molecule, but the details of how conductance changes with symmetry have heretofore been unknown. Herein, we investigate a naphthalenedithiol single-molecule system in which sulfur atoms from the molecule are anchored to two facing gold electrodes. In the studied system, the highest single-molecule conductance, for a molecule junction of 1,4-symmetry, is 110 times larger than the lowest single-molecule conductance, for a molecule junction of 2,7-symmetry. We demonstrate clearly that the measured dependence of molecule junction symmetry for single-molecule junctions agrees with theoretical predictions.

Methane strongly adsorbs on the (110) surface of IrO 2 , a rutile-type metal dioxide. Its C−H bond is facilely dissociated even below room temperature, as predicted in a few theoretical works and actually observed in a recent experimental study. Thence, three questions are posed and answered in this paper: First, why does methane adsorb on the IrO 2 surface so strongly? Second, why is the surface so active for the C−H bond breaking reaction? Third, is there any other rutile-type metal dioxide that is more active than IrO 2 ? A second-order perturbation theoretic approach is successfully applied to the analysis of the electronic structure of methane, which is found to be significantly distorted on the surface. Regarding the first point, it is clarified that an attractive orbital interaction between the surface Ir 5d z 2 orbital and the distorted methane's highest occupied molecular orbital leads to the strong adsorption. As for the second point, the bond strength between the surface metal atom and the CH 3 fragment generated after the C−H bond scission of methane is correlated well with the activation barrier. A substantial bonding interaction between CH 3 's nonbonding orbital and the d z 2 orbital hints at the strong Ir−CH 3 bond and hence high catalytic activity ensues. Last but not least, β-PtO 2 , a distorted rutile-type dioxide, is identified as a more active catalyst than IrO 2 . Here again, a perturbation theoretic line of explanation is found to be of tremendous help. This paper is at the intersection of theoretical, catalytic, inorganic, and physical chemistry. Also, it should serve as a model for the design and study of metal-oxide catalysts for the C−H bond activation of methane.

Site-specific electron transport phenomena through benzene and benzenedithiol derivatives are discussed on the basis of a qualitative Hückel molecular orbital analysis for better understanding of the effect of anchoring sulfur atoms. A recent work for the orbital control of electron transport through aromatic hydrocarbons provided an important concept for the design of high-conductance connections of a molecule with anchoring atoms. In this work the origin of the frontier orbitals of benzenedithiol derivatives, the effect of the sulfur atoms on the orbitals and on the electron transport properties, and the applicability of the theoretical concept on aromatic hydrocarbons with the anchoring units are studied. The results demonstrate that the orbital view predictions are applicable to molecules perturbed by the anchoring units. The electron transport properties of benzene are found to be qualitatively consistent with those of benzenedithiol with respect to the site dependence. To verify the result of the Hückel molecular orbital calculations, fragment molecular orbital analyses with the extended Hückel molecular orbital theory and electron transport calculations with density functional theory are performed. Calculated results are in good agreement with the orbital interaction analysis. The phase, amplitude, and spatial distribution of the frontier orbitals play an essential role in the design of the electron transport properties through aromatic hydrocarbons.