Key Word
表面、分子吸着、電子構造、理論、第一原理計算、多重散乱、エキサイテーション、分光、角度分解電子、X線吸収スペクトル

We study the electronic and magnetic properties of
surfaces, interfaces and novel nanosized materials,
such as TiO2 nanotubes and films or metalorganic molecules.

Through first principles electronic structure methods,
we compute ground state properties and electron spectroscpies,
especially Xray absorption and valence and corelevel
photoelectron emission.

New computational methods based on multiplet and multiple
scattering theory have been developed for Xray absorption and
photoemission spectra.
Research
Recent Topics
Xray absorption spectra of transition metal Ledges calculated with
multichannel multiple scattering theory.
Xray absorption spectroscopy at the transition metal L23edges
is a powerful tool for element specific information about
local coordination, bonding and magnetism.
Due to strong corehole effects, especially multiplet couplings,
oneelectron schemes such as densityfunctional
theory fail to reproduce the spectra and atomic model calculations
are generally used where all extraatomic effects are reduced
to an empirical ligand field.
We have developed a multichannel multiple scattering theory for
L23edge absorption which features the precise electronic structure of
the material through density functional theory, but also
includes the major final state correlation effet, namely
particlehole multiplet coupling. The L23edge of spectra of TiO2
was reproduced correctly for the first time. The "DE" level
splitting, fingerprint of the different crystal phases is shown to
reflect the stacking of the TiO6 octahedra on a length scale of 1 nm.
read article
Electronic structure and corelevel spectra of magnetic films.
Metamagnetic transition in FeRh.
The FeRh ordered alloy switches from the antiferromagnetic state
at low temperature to the ferromagnetic state above 360 K, which
makes it an interesting material for spintronic applications.
We have studied the electronic structure changes across this
"metamagnetic" transition of FeRh films using hard xray photoemission
spectroscopy and firstprinciples calculations.
A significant enhancement of the electronic density of states at the
Fermi level are observed for the ferromagnetic state,
implying that the electronic entropy partially drives the magnetic
transition.
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New computational methods for angleresolved photoemission.
Transition metal surfaces.
A novel realspace multiple scattering
computational method for ultraviolet angle resolved photoemssion and
photoelectron diffraction based on realspace multiple scattering
has been developed.
The interplay between initial and final state effects in ultraviolet
photoemission spectroscopy has been studied for the Cu3d band from Cu(111)
surfaces.
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A first principles method has been developed for angle
and spinresolved resonant photoemission.
The link between spinresolution and circular dichroism in
transition metal resonant photoemission at the 2p3d resonance was
studied. We show that the strong spinpolarization of the photocurrent
observed in certain of antiferromagnetic systems is not a measure
of the local magnetic moments but a consequence of the angular momentum
transfer from the light to the photoelectron spin through
corelevel spinorbit coupling and exchangescattering (Auger decay).
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Defect electronic states in widegap semiconductors probed by
resonant photoelectron diffraction
Oxide semiconductors such as TiO2 have various applications for
optoelectronics, solar energy, catalysis etc.
The band gap states play a major role for transport and
optical properties. We have investigated the defect states at
the ndoped TiO2(110) surface using
resonant photoelectron diffraction,
that is the photoelectron diffraction from the valence defect state
at the Ti2p3d resonance. Thereby the charge distribution of the
defect state could be revealed. By comparing Ovacancy doped and
chemically (Naadsorption) doped surfaces, it is shown that the
defect charge distribution is essentially an intrinsic property
of the Ti(110) surface.
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Organic thin films:
Adsorption and decomposition of single layer Mo(CO)6/Cu
Molybdenum carbonyl Mo(CO)6 was adsorbed on the Cu(111)
surface at 160 K in the monolayer coverage range and studied by scanning
tunneling microscopy. A wellordered monolayer of hexacarbonyl molecules was
observed experimentally for the first time. The monolayer has a hexagonal
structure compatible with a (√7 × √7)R19 superlattice on the copper (111)
plane. The arrangement and orientation of the molecules on the surface were
determined by density functional theory calculations, including van der Waals
interactions. The comparison of adsorption and cohesive energies reveals that
the molecule−substrate interaction is stronger than the intermolecular one,
which
explains the observed twodimensional growth.
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Vibrational properties of copper oxides
Copper oxides are used in catalysis and are the basis of
most hightemperature superconductor materials.
Apart from the abundant tenorite CuO and fcc Cu2O phases,
more exotic phases may be stabilized in nanostructures, among them the
paramelaconite Cu4O3 phase.
Knowledge of the vibrational modes is a prerequiste for the
understanding of thermodynamics and electronphonon coupling.
Using Raman spectroscopy and first principles calculations we have
studied the phonon modes of CuO, Cu2O2 and Cu4O3.
Through a detailed analysis of the displacement
eigenvectors, it is shown that a close relationship exists between
the Raman modes of CuO and Cu4O3.
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Density fluctuations in liquids at the nanoscale
Various thermodynamics quantities are directly linked to the
density fluctuations <n(r) n(r')><n(r)><n(r')> and can be computed as
volume integrals over the paircorrelation function <g(rr')>,
socalled KirkwoodBuff integrals. In the traditional approach
these integrals converge very badly as a function of the upper
integration bound.
We have derived exact expressions for KirkwoodBuff integrals over
finite (hyperspherical) volumes. It is shown that they scale as
1/R with system size and converge much better than the usual
cutoff integrals.
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