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The superexchange interaction between transition-metal ions via oxygen dianion was investigated by the ab initio molecular orbital (MO) method. It is found that the magnitude of the effective exchange integral (J ab) for the CuOCu unit is far larger than those of the NiONi, CrOCr and FeOFe units. Implications of this result are discussed in relation to the high T c superconductivity for Ba-La-Cu-O and R-Ba-Cu-O (R=Y, etc.).

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Unlike most ultrasonic motor designs, in this study, we employ a pair of perpendicular electrodes to energize a piezoelectric vibrator, in which the angle between the direction of polarization and the electric field is purposely set at neither 0 nor 90 so that both the longitudinal and shear effects of the vibrator can be generated simultaneously by a single-phase voltage source. Such a vibrator can generate oblique line trajectories on the contact surface to push a slider for movement, while its moving direction can be easily controlled by switching the excitation sequence of the pair of perpendicular electrodes. In this study, the finite element analysis method was first employed to simulate the oscillatory behavior of the vibrator and then simulation results were verified by single-point, noncontact measurement on the surface of the vibrator. The newly designed linear ultrasonic motor, which can offer identical performance in both forward and backward motions, can maintain its attractive characteristics of simple structure, quiet operation, and single-phase drive. A prototype of the single-phase drive linear ultrasonic motor was fabricated to confirm the feasibility of the proposed vibrator design. The illustrated bidirectional linear ultrasonic motor is shown to be capable of generating a sliding velocity of 84.2 mm/s and a sliding force of 1.79 N. #

Ab initio MO calculations were carried out for diradical, polyradical and cation-radical states of azomethyne-ylide dimer and clusters. The calculated results were applied to a molecular design of possible organic analogues to copper-oxide chains and planes in YBa2Cu3O x and related species. These organic analogues have molecular skeletons similar to those of conducting polymers and graphite, although their electronic structures are quite different because of electron and spin correlations.

The positive holes for copper oxides and isoelectronic species were investigated by the ab initio molecular orbital (MO) method. It is found that the hole is delocalized over the oxide clusters because of the strong 3d σ-2p σ hybridization, and that the spin polarization of the closed-shell pairs is remarkable, indicating an important role of the spin fluctuation for high-T c superconductivity. The extended Hubbard model is necessary for theoretical studies of the hole delocalizations in copper oxides.