ALBERT

Notes: The morphology of the dynamic electron transfer characteristic of chemical reaction dynamics has been studied by introducing the new criterion of an isomorphism of the manifold of electron orbitals at the different points of the reaction coordinate. This criterion is a natural development of the famous Amos–Hall corresponding orbital. Natural orbitals are obtained from the dynamic Fock equation, then it is possible to describe the electronic process of a chemical reaction by the way that the occupation number of an electron orbital changes within the electron orbital manifold which is constructed to have isomorphic equivalency along the reaction coordinate. The electronic process accompanying the chemical reaction CH3+HF → CH4+F has been studied as a demonstration of the present theory. The electron orbital which is transformed by the new criterion is strongly localized, though the transformation operator itself does not contain any explicit localization terms, such as self-energy integrals. The transition of the occupation number inherent to the spatially clamped orbital is clearly demonstrated, and gives a new interpretation of the electronic process of the reaction mechanism. This has also been analyzed in the light of the dynamic electron transfer and dynamic spin transfer characteristic of a chemical reaction.

Notes: The energy of chemical reaction is visualized in real space using the electronic energy density nE(r(vector)) associated with the electron density n(r(vector)). The electronic energy density nE(r(vector)) is decomposed into the kinetic energy density nT(r(vector)), the external potential energy density nV(r(vector)), and the interelectron potential energy density nW(r(vector)). Using the electronic energy density nE(r(vector)) we can pick up any point in a chemical reaction system and find how the electronic energy E is assigned to the selected point. We can then integrate the electronic energy density nE(r(vector)) in any region R surrounding the point and find out the regional electronic energy ER to the global E. The kinetic energy density nT(r(vector)) is used to identify the intrinsic shape of the reactants, the electronic transition state, and the reaction products along the course of the chemical reaction coordinate. The intrinsic shape is identified with the electronic interface S that discriminates the region RD of the electronic drop from the region RA of the electronic atmosphere in the density distribution of the electron gas. If the R spans the whole space, then the integral gives the total E. The regional electronic energy ER in thermodynamic ensemble is realized in electrochemistry as the intrinsic Volta electric potential φR and the intrinsic Herring–Nichols work function ΦR. We have picked up first a hydrogen-like atom for which we have analytical exact expressions of the relativistic kinetic energy density nTM(r(vector)) and its nonrelativistic version nT(r(vector)). These expressions are valid for any excited bound states as well as the ground state. Second, we have selected the following five reaction systems and show the figures of the nT(r(vector)) as well as the other energy densities along the intrinsic reaction coordinates: a protonation reaction to He, addition reactions of HF to C2H4 and C2H2, hydrogen abstraction reactions of NH3+ from HF and NH3. Valence electrons possess their unique delocalized drop region remote from those heavily localized drop regions adhered to core electrons. The kinetic energy density nT(r(vector)) and the tension density τ(vector)S(r(vector)) can vividly demonstrate the formation of the chemical bond. Various basic chemical concepts in these chemical reaction systems have been clearly visualized in real three-dimensional space. © 2001 American Institute of Physics.

Notes: The microhardness of C70 crystals was investigated in the temperature range of 295–425 K. The hardness gradually decreased with increasing temperature. The photoinduced hardening was observed after the long-time illumination of light. The hardening reached the maximum near the phase transition temperature of 348 K. These results are discussed and compared with those of C60 crystals. © 2001 American Institute of Physics.

Notes: We address the intramolecular vibronic interactions in the C36 tri- and tetra-anions to understand the Jahn–Teller effects and possible superconductivity in "electron-doped" C36 solids. We use the B3LYP hybrid Hartree–Fock/density-functional-theory method for our theoretical analyses. Neither the highest occupied molecular orbital (HOMO) nor the lowest unoccupied molecular orbital (LUMO) of the C36 molecule with D6h symmetry are degenerate, but the next LUMO is twofold degenerate. One can therefore expect Jahn–Teller distortions and interesting electronic properties in the C36 anions. Computed vibronic and electron–phonon coupling constants of the tetra-anion are about twice as large as those of the tri-anion. The second lowest Jahn–Teller active E2g mode of 561 cm−1 is predicted to have the largest coupling constants in both anions. We calculate superconducting transition temperature Tc from McMillan's formula using the coupling constants as well as electronic densities of states at the Fermi level and Coulomb pseudopotentials as parameters. © 1999 American Institute of Physics.

Notes: Based on numerical solutions for the transmission characteristics of a typical quantum waveguide (the T-structure and its modifications), some effects of practical importance, the finiteness of confinement potential and the geometrical deviations from the ideal shape, are clarified. Numerical results are also compared with those of the simplified S-matrix method and the applicability of the latter is discussed. The results may be useful in applying a quantum waveguide to electronic devices and in analyzing more complex structures by the simplified S-matrix. © 1996 American Institute of Physics.

Notes: This paper presents a new simple algorithm that guarantees simultaneous conservation of energy, linear momentum, and angular momentum of a whole system in reaction dynamics calculations, employing atomic Cartesian coordinates. We apply this algorithm to the reaction dynamics in the NH3++NH3 system. We show that along the intrinsic reaction coordinate (IRC) of the hydrogen abstraction (HA) channel of the reaction, the geometries of local minima and transition state (TS) change appreciably with the rotational energy due to the angular momentum. Reaction dynamics calculations in the vicinity of the IRC reveal the dynamical effects that the angular momentum promotes or suppresses the reaction. © 1999 American Institute of Physics.

Notes: Cathodoluminescence (CL) spectra of diamond films epitaxially grown on single crystal platinum (111) have been investigated at room temperature and 89 K. It was found that the CL spectra of the heavily boron-doped (〉3×1020 cm−3) diamond films of more than 16 μm thickness consist only of a near-edge emission at 248±1 nm (5.00±0.02 eV), while any mid-gap emissions are absent. That result suggests that few defects are in the films. It was also found that the temperature dependence of the 248 nm band is very unique, since its intensity increases as temperature increases. The mechanism of the 248 nm band seems to involve quasi-direct transition. © 1998 American Institute of Physics.

Notes: Luminescence spectra and their variation with temperature have been investigated for solid films of poly(methylphenylsilane) and its branched analogs. Introduction of branching points to the polymers enhances the broad luminescence band in the visible region while suppressing the sharp UV luminescence band due to the resonant recombination of the exciton. The intensity of the visible luminescence is observed to keep on increasing with decreasing temperature in contrast with the nearly temperature-independent intensity of the resonant luminescence. The behavior is interpreted in terms of phonon-assisted tunneling between luminescence centers and nonradiative ones. © 1995 American Institute of Physics.

Notes: Diamond films of various thicknesses (1.5–12 μm) deposited on Pt (111) by microwave enhanced chemical vapor deposition (CVD) were studied by scanning electron microscopy (SEM) observation and x-ray diffraction pole figure measurements. The dependence of the surface morphology and structure of the films on the film thickness were investigated. It was observed by SEM that the coalescence between neighboring (111) diamond surface became more significant as the film thickness increased. It was revealed by the x-ray diffraction measurements that the 〈111〉 texture of the diamond films improved with increasing film thickness, whereas azimuthal alignment of the crystals was roughly independent of the film thickness. It was also found that the deposited films contained epitaxial diamond crystals which were azimuthally rotated by 60° about the [111] axis of the samples. With increasing film thickness, the ratio of the 60°-rotated crystals to nonrotated crystals increased, which is primarily attributed to twin formation during growth of the CVD diamond on its (111) surface. © 1997 American Institute of Physics.

Notes: The influence of external stresses on a crystallization and a precipitation process for amorphous WSi2.6 films has been studied. An as-deposited amorphous WSi2.6 has crystallized as a hexagonal WSi2 by annealing at 400 °C for 1 h, and excess Si has precipitated to the WSi2/substrate interface. To verify whether the driving force of the precipitation to the interface is a stress relaxation, calculations of the volume change by a crystallization, precipitations (in the film and to the interface), and the stress measurement were performed. It was revealed that as-deposited film had a tensile stress, and it increased by precipitation of excess Si to the interface. That is, the driving force of the precipitation to the interface is not the stress relaxation. Then we tried to apply larger stress (compression and tension) to make clear an effect of stress on the structural change. By annealing at 350 °C under external tensile stress,the Si precipitated at the interface was not observed.On the other hand, by annealing under external compressive stress, a greater amount of Si has precipitated than that without external stress. These phenomena seem to be related to the stress-assisted diffusion similar to Nabarro–Herring creep.