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Seiji Kojima
University of Tsukuba
584Publications
29H-index
4,192Citations
Publications 578
Newest
#1Seiji KojimaH-Index: 29
#2AftabuzzamanH-Index: 2
Last.Wolfgang KleemannH-Index: 37
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#1T. MoriH-Index: 19
Last.Seiji KojimaH-Index: 29
view all 11 authors...
Disordered systems exhibit universal excitation, referred to as the boson peak, in the terahertz region. Meanwhile, the so-called fracton is expected to appear in the nanoscale region owing to the self-similar structure of monomers in polymeric glasses. We demonstrate that such excitations can be detected using terahertz spectroscopy. For the interaction between terahertz light and the vibrational density of states of the fractal structure, we formulate an infrared light-vibration coupling coeff...
#1T. Mori (University of Tsukuba)H-Index: 19
#2Leona Motoji (University of Tsukuba)
Last.Seiji Kojima (University of Tsukuba)H-Index: 29
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Terahertz time-domain spectroscopy has been applied to protein myoglobin dried sample. The boson peak (BP) which is a universal excitation of disordered system has been detected around 0.5 THz. While, fracton will be a universal excitation in the self-similar structure, and it has been observed above the BP frequency. How the fracton appear in the infrared spectrum is explained using the fracton model and the linear response theory for amorphous materials.
Source
#1Mirza H. K. Rubel (RU: University of Rajshahi)H-Index: 6
#2M. E. Hossain (RU: University of Rajshahi)
Last.Seiji Kojima (University of Tsukuba)H-Index: 29
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Potassium triniobate (KNb3O8) ceramic powder has been synthesized by a novel aqueous organic gel route relatively at low calcination temperature above 700 °C. Initially, homogeneous K-Nb precursor gels were prepared using the starting materials K-EDTA and Nb-citrate complex. Afterward, the mixture in stoichiometric ratio of K, Nb, and citric acid produced a pale yellow viscous like gel from which precursor powder was obtained after prolonged heating at 80 °C. The X-ray diffraction patterns revea...
Source
#1Md. Mijanur Rahaman (CIS: Carnegie Institution for Science)
#2Mirza H. K. Rubel (RU: University of Rajshahi)H-Index: 6
Last.Nobuhiro KumadaH-Index: 26
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Abstract Density functional theory (DFT) based first-principles calculations using GGA+U method have been performed for the first time to investigate elastic, electronic, optical, thermodynamic properties including charge density, Fermi surface, Mulliken population analysis, and theoretical Vickers hardness of the newly synthesized LiCuBiO 4 (LCBO) compound. The calculated structural parameters are in good agreement with available experimental results, which assessed the reliability of our calcu...
Source
#1Seiji Kojima (University of Tsukuba)H-Index: 29
#2V. N. Novikov (Technische Universität Darmstadt)H-Index: 15
Last.Osamu Yamamuro (UTokyo: University of Tokyo)H-Index: 24
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Abstract This paper reports the variation in the first sharp diffraction peak (FSDP) and the boson peak (BP) of lithium and cesium borate glasses xM2O-(1-x)B2O3 (M = Li and Cs, x = 0.08. 0.14, and 0,22) investigated by elastic and inelastic neutron scattering. The different content dependences between lithium and cesium borate glasses are discussed on the basis of the different modifications of the boron-oxide network structure by the small Li and large Cs ions. The static characteristic correla...
Source
Numerous physical properties of CaPd3Ti4O12 (CPTO) and CaPd3V4O12 (CPVO) double perovskites have been explored based on density functional theory (DFT). The calculated structural parameters fairly agree with the experimental data to confirm their stability. The mechanical stability of these two compounds was clearly observed by the Born stability criteria. To rationalize the mechanical behavior, we investigate elastic constants, bulk, shear and Young's modulus, Pugh's ratio, Poisson's ratio and ...
#1T. MoriH-Index: 19
#2Mikitoshi KabeyaH-Index: 2
Last.Seiji KojimaH-Index: 29
view all 8 authors...
#1T. MoriH-Index: 19
#2Yuta IijimaH-Index: 1
Last.Seiji KojimaH-Index: 29
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