Electronic properties of transuranium compounds with HoCoGa-type tetragonal crystal structure

Maehira, Takahiro*; Hotta, Takashi; Ueda, Kazuo*; Hasegawa, Akira*

New Journal of Physics (Internet), 8(2), p.24_1 - 24_20, 2006/02

https://doi.org/10.1088/1367-2630/8/2/024

By using a relativistic band-structrue calculation method, we investigate energy band structures and the Fermi surfaces of NpTGa, PuTGa, and AmCoGa with transition metal atoms T. It is found in common that the energy bands in the vicinity of the Fermi level are mainly due to the large hybridization between and Ga electrons. For PuTGa, we observe several cylindrical sheets of Fermi surfaces with large volume for T=Co, Rh, and Ir. It is also found that the Fermi surfaces of NpFeGa, NpCoGa, and NpNiGa are similar to those of UCoGa, UNiGa, and PuCoGa, respectively, except for small details. For AmCoGa, the Fermi surfaces are found to consist of large cylindrical electron sheets and small closed hole sheets, similar to PuCoGa. The similarity is basically understood by a rigid-band picture.

Quasi-two-dimensional Fermi surfaces in the flat antiferromagnetic Brillouin zone of NpRhGa studied by dHvA experiments and energy band calculations

Aoki, Dai*; Yamagami, Hiroshi*; Homma, Yoshiya*; Shiokawa, Yoshinobu; Yamamoto, Etsuji; Nakamura, Akio; Haga, Yoshinori; Settai, Rikio*; Onuki, Yoshichika

Journal of Physics; Condensed Matter, 17(17), p.L169 - L175, 2005/05

https://doi.org/10.1088/0953-8984/17/17/L03

no abstracts in English

calculation of magnetic resonant X-ray scattering spectra in NiO

Usuda, Manabu; Takahashi, Manabu*; Igarashi, Junichi

Physical Review B, 69(1), p.014408_1 - 014408_7, 2004/01

https://doi.org/10.1103/PhysRevB.69.014408

We have investigated the magnetic X-ray scattering spectra around the edge of Ni in antiferromagnetic NiO on the basis of an calculation. By taking account of orbital polarization through the spin-orbit interaction, we reproduce well the spectra obtained experimentally. We have analyzed the contributions of the resonant dipolar, quadrupolar, and non-resonant scattering processes and clarified the mechanism of the resonant magnetic X-ray scattering.

Sulfur-doping of rutile-titanium dioxide by ion implantation; Photocurrent spectroscopy and first-principles band calculation studies

Umebayashi, Tsutomu; Yamaki, Tetsuya; Yamamoto, Shunya; Miyashita, Atsumi; Tanaka, Shigeru; Sumita, Taishi*; Asai, Keisuke*

Journal of Applied Physics, 93(9), p.5156 - 5160, 2003/05

https://doi.org/10.1063/1.1565693

Sulfur (S)-doped titanium dioxide (TiO) was synthesized by ion implantation and subsequent thermal annealing. Compared to the pure TiO, a photocurrent was observed in the lower energy regions for the S-doped TiO. Based on the theoretical analyses by the first principles band calculations using the full potential linearized augmented plane wave methods within the generalized gradient approximation, the mixing of the S 3p states with the valence band (VB) was found to contribute to the increasing width of the VB. This leads to the bandgap narrowing in the S-doped TiO. Therefore, the photon-to-carrier conversion was induced during irradiation by visible light above 420 nm ( 2.9 eV).

Electronic structure and the fermi surface of UTGa (T=Fe, Co, Rh)

Maehira, Takahiro; Higuchi, Masahiko*; Hasegawa, Akira*

Physica B; Condensed Matter, 329-333(1-4), p.574 - 575, 2003/05

https://doi.org/10.1016/S0921-4526(02)02450-X

The relativistic energy-band calculations have been carried out for , and under the assumption that 5-electrons are itinerant. A hybridization between the U 5 state and Ga 4 state occurs in the vicinity of the Fermi level. The Fermi surface of is quite similar to that of , which are all small in size and closed in topology. has the quasi-two-dimensional Fermi surface which looks like a lattice structure.

Analysis of electronic structures of 3d transition metal-doped TiO based on band calculations

Umebayashi, Tsutomu; Yamaki, Tetsuya; Ito, Hisayoshi; Asai, Keisuke*

Journal of Physics and Chemistry of Solids, 63(10), p.1909 - 1920, 2002/10

https://doi.org/10.1016/S0022-3697(02)00177-4

The electronic structures of titanium dioxide (TiO) doped with 3d transition metals (V, Cr, Mn, Fe, Co and Ni) have been analyzed by ab-initio band calculations based on the density functional theory with the full-potential linearized-augmented-plane-wave methods. When TiO is doped with V, Cr, Mn, Fe or Co, an occupied level occurs and the electrons localized around each dopant. As the atomic number of the dopant increases, the localized level shifts to lower energy. In contrast, the electrons from Ni dopant are somewhat delocalized, thus significantly contributing to the formation of the valence band with O p and Ti 3d electrons. Based on a comparison with the absorption and photoconductivity data previously reported, we show that the t state of the dopant plays a significant role in the photoresponse of TiO under visible light irradiation.

Fermi surface of heavy Fermion compounds CeTIn (T=Rh, Ir, and Co); Band-calculation and tight-binding approach

Maehira, Takahiro; Takimoto, Tetsuya; Hotta, Takashi; Ueda, Kazuo*; Higuchi, Masahiko*; Hasegawa, Akira*

Journal of the Physical Society of Japan, Vol.71, Supplement, p.285 - 287, 2002/00

https://doi.org/10.1143/JPSJS.71S.285

Recently a new family of Ce-based heavy fermion superconductor (T=Rh, Ir, and Co) has been reported. The dHvA effect has been successfully observed in and .The angular dependence of dHvA branches is well explained by a quasi-two dimensional Fermi surface(F.S.). In order to clarify band structures of Ce-115 systems such as CeIrIn and CeCoGa, two-step strategy is here employed. In the first step, the F.S. are derived by using the RLAPW method. In the next step, the band structure near the Fermi level is reanalyzed by using a simple tight-binding model. Namely, hopping amplitudes of -electrons between neighboring Ce ions are parameterized to reproduce the F.S. obtained in the band-calculation. By further adding the Coulomb interaction terms into this tight-binding model, a simple many-body Hamiltonian for Ce-compounds can be constructed. This Hamiltonian opens a way to discuss magnetism and superconductivity in -electron systems from the microscopic viewpoint.

A study on properties of uranium oxide using band theory

Tejima, Shogo

JNC TN8400 2000-029, 54 Pages, 2000/10

JNC-TN8400-2000-029.pdf:1.32MB

This report describes the study done by the author as a postdoctoral research associate at Japan Nuclear Cycle Development Institute. This report is divided into three parts: construction of a relativistic band calculation formalism based on the density functional theory, using this method, investigation of the electrical properties for ferromagnetic UGe and antiferromagnetic UO. (1)A relativistic band calculation (RBC) method. Band calculations for the s, p, and d electric structure have been developed well in the practical application and theoretical study. But band calculation method treating magnetic 5f electrons as actinide compounds are complicated and needed relativistic approach, so it is behind with the study of the 5f system. In this study we construct the relativistic band calculationformalism valid for magnetic 5f electrons. (2)Electric properties of UGe. The actinide compounds UGe is ferromagnetic, so the theoretical analysis is not well yet. The electric structure and fermi surface of UGe are analyzed using the RBC. The theoretical results show that UGe is heavy electron with the 5f character and are agreement with experimental one. (3)Electric structure of nuclear fuel UO. It is important to understand the mechanism of the thermal conductivity of nuclear fuel as antiferromagnetic UO. The UO band calculation reflecting the thermal properties, into account of relativistic effect, have not done yes. So using the RBC the detailed electric structure of UO are obtained.