Ab initio MO Studies on the Correlation and Spin Correlation Effects for Copper-Oxygen and Copper-Halogen Bonds in High-T_c Copper Oxide Superconductors

Abstract

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. #

N‐band Hubbard models for copper oxides and isoelectronic systems. New models for organic and organometallic magnetic conductors and superconductors

“…Eq. (9). The JNiNi values by both the CI and perturbation methods increase with the decrease of Apd(0).…”

“…The theoretical studies [8][9][10][11]14, 151 of undoped transition metal oxides have provided the working hypothesis (WH) I as WH I : Undoped precursors for the high-T, superconductivity belong to the CT semiconductors with small CT energies Apd(0).…”

“…This is not at all surprising since copper oxide belongs to the intermediate correlation regime as has been elucidated by the ab initio computations [9-111. Figure 3 illustrates the overall pictures obtained by our recent ab initio and N-band model calculations [8][9][10][11]14,151.…”

“…In this section, theoretical aspects of transition metal oxides and halides are briefly summarized [8][9][10][11]14,151. The undoped copper oxide La,CuO, belongs to the K,NiF,-type solids, which are typical two-dimensional (2D) antiferromagnets such as La,NiO, [ 16,171.…”

“…It is also noteworthy that the relative stability is dependent on several factors such as the cluster size, crystal structure, hole concentration, Madelung potential, etc. Therefore, previous ab initio calculations [8][9][10][11]26,36] of the CuO, and MOM clusters are not conclusive enough yet to elucidate the relative stability between the (T-and rr-ground states of doped copper-oxide crystals. More larger clusters, where the screening of the 3d-2p valence correlation (i.e., t < 1 .O in the present model) occurs should be examined to settle this problem at an ab initio level as has been pointed out previously [ …”