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20 results on '"Okada, J. T."'

1. Visualizing the mixed bonding properties of liquid boron with high resolution Compton scattering

Author

Okada, J. T., Sit, P. H. -L., Watanabe, Y., Barbiellini, B., Ishikawa, T., Wang, Y. J., Itou, M., Sakurai, Y., Bansil, A., Ishikawa, R., Hamaishi, M., Paradis, P. -F., Kimura, K., and Nanao, S.

Subjects
Condensed Matter - Materials Science
Abstract

Bonding characteristics of liquid boron at 2500K are studied by using high resolution Compton scattering. An excellent agreement is found between the measurements and the corresponding Car-Parinello molecular dynamics simulations. Covalent bond pairs are clearly shown to dominate in liquid boron along with the coexistence of diffuse pairs. Our study reveals the complex bonding pattern of liquid boron, and gives insight into the unusual properties of this high temperature liquid.

Published
2015
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2. Persistence of Covalent Bonding in Liquid Silicon Probed by Inelastic X-ray Scattering

Author

Okada, J. T., Sit, P. H. -L., Watanabe, Y., Wang, Y. J., Barbiellini, B., Ishikawa, T., Itou, M., Sakurai, Y., Bansil, A., Ishikawa, R., Hamaishi, M., Masaki, T., Paradis, P. -F., Kimura, K., and Nanao, S.

Subjects
Condensed Matter - Materials Science
Abstract

Metallic liquid silicon at 1787K is investigated using x-ray Compton scattering. An excellent agreement is found between the measurements and the corresponding Car-Parrinello molecular dynamics simulations. Our results show persistence of covalent bonding in liquid silicon and provide support for the occurrence of theoretically predicted liquid-liquid phase transition in supercooled liquid states. The population of covalent bond pairs in liquid silicon is estimated to be 17% via a maximally-localized Wannier function analysis. Compton scattering is shown to be a sensitive probe of bonding effects in the liquid state., Comment: 5pages, 3 postscript figures

Published
2012
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4. Thermoelectric properties of polygrained icosahedral Al71-xGaxPd20Mn9 (x=0,2,3,4) quasicrystals.

Author

Takagiwa, Y., Kamimura, T., Hosoi, S., Okada, J. T., and Kimura, K.

Subjects
THERMOELECTRICITY, QUASICRYSTALS, ELECTRIC conductivity, THERMAL electromotive force, THERMAL conductivity, GALLIUM
Abstract

The electrical and thermal transport properties of quaternary icosahedral Al71-xGaxPd20Mn9 (x=0,2,3,4) quasicrystals, obtained by replacing Al in icosahedral Al–Pd–Mn quasicrystal with Ga, have been measured in accordance with the guiding principle of “weakly bonded rigid heavy clusters” (WBRHCs). While the electrical conductivity and Seebeck coefficient were not dramatically changed, the thermal conductivity effectively decreased with increasing Ga concentration except for the sample with x=4. Although the thermoelectric properties do not obey the WBRHCs, the dimensionless figure of merit increased by a factor of 1.4 from 0.18 for Al71Pd20Mn9 to 0.26 for Al68Ga3Pd20Mn9 quasicrystal. [ABSTRACT FROM AUTHOR]

Published
2008
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5. Visualizing the Mixed Bonding Properties of Liquid Boron with High-Resolution X-Ray Compton Scattering

Author

Okada, J. T., primary, Sit, P. H.-L., additional, Watanabe, Y., additional, Barbiellini, B., additional, Ishikawa, T., additional, Wang, Y. J., additional, Itou, M., additional, Sakurai, Y., additional, Bansil, A., additional, Ishikawa, R., additional, Hamaishi, M., additional, Paradis, P.-F., additional, Kimura, K., additional, and Nanao, S., additional

Published
2015
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6. Persistence of Covalent Bonding in Liquid Silicon Probed by Inelastic X-Ray Scattering

Author

Okada, J. T., primary, Sit, P. H.-L., additional, Watanabe, Y., additional, Wang, Y. J., additional, Barbiellini, B., additional, Ishikawa, T., additional, Itou, M., additional, Sakurai, Y., additional, Bansil, A., additional, Ishikawa, R., additional, Hamaishi, M., additional, Masaki, T., additional, Paradis, P.-F., additional, Kimura, K., additional, and Nanao, S., additional

Published
2012
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13. Structural vacancies in Al-Pd-Mn quasicrystal and its (1/1, 2/1)-AlPdMnSi approximant crystals: Positron lifetime studies.

Author

Takagiwa, Y., Okada, J. T., Kimura, K., Kitahata, H., Matsushita, Y., and Kanazawa, I.

Subjects
*POSITRON annihilation, *POSITRONS, *CRYSTALS, *CRYSTALLOGRAPHY, *QUASICRYSTALS
Abstract

Positron annihilation lifetimes of the stable icosahedral (i) Al-Pd-Mn quasicrystal and its (1/1, 2/1)-AlPdMnSi and 1/0-Al12Re approximant crystals were measured at ambient temperature. The observed single-lifetime of the i-Al-Pd-Mn quasicrystal is very close to that of the (1/1, 2/1)-AlPdMnSi approximant crystals, indicating that the same type of structural vacancies exists in all these specimens. On the other hand, the lifetime of 1/0-Al12Re approximant crystal, which has no structural vacancies, is significantly shorter than the above results. We discuss the relationship between the positron lifetimes and mean valence-electron density. [ABSTRACT FROM AUTHOR]

Published
2008
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14. HAADF-STEM study of B-Mg-Ru approximant crystals.

Author

Miyazaki, Y., Okada, J. T., Abe, E., and Kimura, K.

Subjects
*CRYSTALS, *CRYSTALLOGRAPHY, *ELECTRON microscopy, *MICROSCOPY, *SCANNING electron microscopy
Abstract

Two-dimensional structures of decagonal approximant crystals have been studied in a B-Mg-Ru system where decagonal quasicrystals have been predicted. High-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM) imaging confirms that four approximant phases, which form at high temperatures, can be described as tessellations of hexagon and boat subunits with the same atomic decorations as B11Mg5Ru13. The images also support the existence of bow-tie flip structures in the all four approximant crystals. Long periodicities in one direction up to 8.5 nm are interpreted to be caused by modulation of rows of boat tiles. [ABSTRACT FROM AUTHOR]

Published
2008
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18. SOMINT: An Improved Model for Studying Conducting Objects Near Lossy Half-Spaces.

Author

CALIFORNIA UNIV LIVERMORE LAWRENCE LIVERMORE LAB, Brittingham,J N, Miller,E K, Okada,J T, CALIFORNIA UNIV LIVERMORE LAWRENCE LIVERMORE LAB, Brittingham,J N, Miller,E K, and Okada,J T

Abstract

This report summarizes the development of a moment-method numerical code to study wire antennas near lossy earth. The computation time of this code is greatly reduced by two new methods for evaluating the Sommerfeld integrals. In the evaluation of the integrals off the earth, a bivariate interpolation scheme on a prestored grid is shown to give very quick and accurate results. A new series solution is presented to evaluate the integral for values near the interface. Test results of this program are given, along with extensive numerical data on vertical half-rhombic and sloping V antennas. (Author)

Published
1978

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