Friction of a single molecule chemisorbed on a surface is a very fundamental property related to the dynamics of the diffusion of the molecule. We used a newly developed method, in which energy-controlled rare gas ato...
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Friction of a single molecule chemisorbed on a surface is a very fundamental property related to the dynamics of the diffusion of the molecule. We used a newly developed method, in which energy-controlled rare gas atoms collide with CO molecules on a stepped surface to displace CO molecules from initial terrace sites to final step sites. The friction coefficient of CO molecules on the surface was determined directly by comparing the experimentally measured increase in the number of CO molecules at step sites with classical molecular dynamics simulation results.
To evaluate whether chronic impacts on biota are caused by continuous 50 Mton CO 2 injection per year into the ocean, we simulated transport and dilution of the injected CO 2 using an offline ocean general circulati...
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To evaluate whether chronic impacts on biota are caused by continuous 50 Mton CO 2 injection per year into the ocean, we simulated transport and dilution of the injected CO 2 using an offline ocean general circulation model (OGCM) with a horizontal resolution of 0.1 by 0.1 degrees. Carbon dioxide is continuously injected during 30 years into a site with one degree in longitude and three degrees in latitude. Since most of CO 2 dissolved water is transported in the longitudinal direction, its broad latitudinal width is effective to decrease CO 2 concentration in order to reduce/avoid biological impacts. CO 2 concentration increases in the first several to 10 years, but it has an upper limit after the initial increase. Since the simulated maximum CO 2 concentration is 80 percents of the "predicted no effect concentration" (PNEC), an index to estimate concentration causing no effects on biota, we can expect that continuous 50 Mton/year CO 2 injection causes no chronic impacts.
We discuss bias voltage effects on the elastic and the inelastic currents in the tunneling region. We have derived and solved two self-consistent loops: one for electron-electron interaction within the Hartree-Fock ap...
We discuss bias voltage effects on the elastic and the inelastic currents in the tunneling region. We have derived and solved two self-consistent loops: one for electron-electron interaction within the Hartree-Fock approximation, and another for the electron-intramolecular vibration coupling within the Born approximation. The formalism is based on Keldysh Green’s function theory; numerical calculations were made in terms of ab initio quantum chemistry techniques augmented with a model for the electrodes. While no remarkable voltage effect on the vibronic currents was found in the low-bias voltage region, we found significant bias voltage effect in the high-bias voltage region. The suppressive correlation between the elastic and the inelastic components of the current is reduced because of the molecular orbital energy shift in the latter region.
We have studied the lineshape of the inelastic electron tunneling spectroscopy (IETS) theoretically. In order to calculate vibronic currents including the inelastic effect, we have adopted the Keldysh Green’s functio...
We have studied the lineshape of the inelastic electron tunneling spectroscopy (IETS) theoretically. In order to calculate vibronic currents including the inelastic effect, we have adopted the Keldysh Green’s function method and the self-consistent Born approximation, which is applied to the electron-intramolecular-vibration couplings. The second derivative of the vibronic current taken against the bias voltage has peak and dip structures in the IETS. In this paper, we discuss intrinsic and extrinsic mechanisms which control and modify the lineshape of the IETS. The effect of the intrinsic physical parameters, i.e., the contact transfer integral between the molecule and the electrode and the energy gap between the molecular orbital energy and the Fermi level of the electrode, on the lineshape will be discussed first. Next, we will discuss an extrinsic factor, i.e., the effect of the macroscopic shape of the electrode. In order to take into account the shape effect, we use the envelope function method. Our theoretical study will be useful as a guideline to understand various lineshapes of the IETS observed in various experimental situations.
A GW approximation (GWA) method named U+GWA is proposed, where we can start GWA with more localized wave functions obtained by the local spin-density approximation (LSDA)+U method. Then GWA and U+GWA are applied to Mn...
A GW approximation (GWA) method named U+GWA is proposed, where we can start GWA with more localized wave functions obtained by the local spin-density approximation (LSDA)+U method. Then GWA and U+GWA are applied to MnO, NiO, and V2O3 in antiferromagnetic phase. The band gaps and energy spectra show excellent agreement with the experimentally observed results and are discussed in detail. The calculated width of d bands of V2O3 is much narrower than that of the observed one which may be a mixture of t2g2 multiplet and single-electron t2g level. GWA or U+GWA does not work also in the paramagnetic phase of V2O3 and the reason for this is clarified. The method of the unique choice of on-site Coulomb interaction is discussed in detail. The criterion for whether we should adopt GWA or U+GWA is discussed and is assessed with the help of the off-diagonal elements of the self-energy.
We have constructed a LDA+DMFT method in the framework of the iterative perturbation theory with local density approximation (full-LDA) Hamiltonian without mapping onto the effective Wannier orbitals. We then apply th...
We have constructed a LDA+DMFT method in the framework of the iterative perturbation theory with local density approximation (full-LDA) Hamiltonian without mapping onto the effective Wannier orbitals. We then apply this LDA+DMFT method to ferromagnetic bcc Fe and fcc Ni as a test of transition metal, and to antiferromagnetic NiO as an example of transition metal oxide. In Fe and Ni, the width of occupied 3d bands is narrower than those in LDA and Ni 6 eV satellite appears. In NiO, the resultant electronic structure is of charge-transfer insulator type and the band gap is 4.3 eV. These results are in good agreement with the experimental x-ray photoemission spectroscopy. The configuration mixing and dynamical correlation effects play a crucial role in these results.
We have performed an in situ photoemission study of Pr1−xCaxMnO3 (PCMO) thin films grown on LaAlO3 (001) substrates and observed the effect of epitaxial strain on the electronic structure. We found that the chemical p...
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We have performed an in situ photoemission study of Pr1−xCaxMnO3 (PCMO) thin films grown on LaAlO3 (001) substrates and observed the effect of epitaxial strain on the electronic structure. We found that the chemical potential shifted monotonically with doping, unlike bulk PCMO, implying the disappearance of incommensurate charge fluctuations of bulk PCMO. In the valence-band spectra, we found a doping-induced energy shift toward the Fermi level (EF) but there was no spectral weight transfer, which was observed in bulk PCMO. The gap at EF was clearly seen in the experimental band dispersions determined by angle-resolved photoemission spectroscopy and could not be explained by the metallic band structure of the C-type antiferromagnetic state, probably due to localization of electrons along the ferromagnetic chain direction or due to another type of spin-orbital ordering.
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