Kenichi Kojima

Neutron and X-Ray Diffraction Studies of a Valence Fluctuating Compound YbInCu4

The crystal structure of YbInCu 4 has been refined by the Rietveld analysis of TOF neutron powder diffraction data. This compound has a cubic AuBe 5 (C15b, F\bar43m)-type structure with the lattice constant a =7.1575(6) A, and Yb ions are completely ordered at the 4c site. X-ray powder diffraction data have also been taken as a function of temperature. The lattice constant shows an abrupt change of 0.15% at the temperature of Yb valence phase transition (about 40 K) without any change in the crystal symmetry.

Characterization of Grown-in Dislocations in Benzophenone Single Crystals by X-Ray Topography

Benzophenone single crystals were grown by the Czochralski method. The dislocations introduced during the crystal growth were examined using X-ray topography. Double images of single dislocations were found on the topographs taken in some reflection planes. The Burgers vector of predominant grown-in dislocations was estimated from analysis of the dislocation images on the basis of kinematical theory.

ESR and Magnetic Susceptibility in Y2BaCuO5

ESR and magnetic susceptibility measurements were made in insulating Y2BaCuO5. A uniaxial type of the ESR spectrum was observed at room temperature and was found to be due to Cu2+ ions by an intensity measurement. The g values parallel and perpendicular to the symmetry axis are 2.24±0.02 and 2.06±0.02, respectively. Susceptibility measurements showed that the Curie constant is (0.22±0.1) emuK/mol and the paramagnetic Curie temperature is (-8±1) K. The small value of the Curie constant suggests that the sample contains some oxygen deficiency.

Improvement of crystal quality for tetragonal hen egg white lysozyme crystals under application of an external alternating current electric field

X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white lysozyme (HEWL) crystals grown with and without application of an external alternating current (AC) electric field, and then the crystal quality was assessed by the FWHMs of each rocking-curve profile. The FWHMs for HEWL crystals grown with an external electric field were smaller than those for crystals grown without. In particular, the average FWHM for the 12 12 0 reflection with an external electric field (0.0034°) was significantly smaller than that without (0.0061°). This indicates that the crystal quality of HEWL crystals was improved by application of the external AC electric field. This crystallization technique can be expected to enhance the resolution of protein molecule structure analysis by X-ray diffraction.

Temperature dependence of microhardness of tetragonal hen-egg-white lysozyme single crystals

The mechanical properties of high-quality single crystals of tetragonal hen-egg-white lysozyme from hen egg white were investigated by the indentation method. The indentation marks were clearly observed on the crystal surface and elastic recovery did not occur. The micro-Vickers hardness of the crystals in the wet condition was observed to be 20 MPa at room temperature. To investigate deformation, the temperature dependence of the hardness was investigated from 278 to 308 K. The hardness strongly depended on the temperature above 290 K. From these results the deformation of lysozyme single crystals was explained in terms of dislocation mechanisms.

Infrared and Raman Study of (La1-xSrx)2NiO4 and La2(Ni1-xCux)O4

Motivated by the observation of the close correlation between disappearance of the infrared absorption peak at about 680 cm -1 and the appearance of high- T c superconductivity in (La 1- x M x ) 2 CuO 4 (M=Ca, Sr, and Ba), we have measured infrared absorption spectra of (La 1- x Sr x ) 2 NiO 4 ( x =0.0, 0.01, 0.02, 0.03 0.04, 0.07, 0.10 and 0.15), La 2 (Ni 1- x Cu x )O 4 ( x =0.0, 0.20, 0.40 0.60, 0.70, 0.80, 0.85, 0.90, 0.95 and 1.00), and Raman spectrum of La 2 NiO 4 . No disappearance of the infrared absorption peak at about 680 cm -1 has been observed in (La 1- x Sr x ) 2 NiO 4 . By assigning the peaks to characteristic lattice vibrational modes, discussions have been devoted to the possible origin of the infrared anomaly.

Crystallization of high-quality protein crystals using an external electric field

The effect of a 20 kHz external electric field on the quality of tetragonal hen egg white (HEW) lysozyme crystals was investigated using X-ray diffraction rocking-curve measurements. The full width at half-maximum was found to be larger for high-order reflections but smaller for low-order reflections. In particular, it was revealed that a large amount of local strain is accumulated in tetragonal HEW lysozyme crystals grown under an applied field at 20 kHz. Comparison with previous results obtained for crystals grown with an applied field at 1 MHz [Koizumi, Uda, Fujiwara, Tachibana, Kojima & Nozawa (2013). J. Appl. Cryst. 46, 25–29] indicated that improvement of the protein crystal quality could be achieved by selection of an appropriate frequency for the applied electric field, which has a significant effect on the growth of the solid.

Synthesis of Single-Wall Carbon Nanotubes from Diesel Soot

We show that diesel soot can be recycled as a carbon source for the synthesis of single-wall carbon nanotubes (SWNTs). The synthesis of SWNTs was carried out by the laser vaporization of diesel soot. The presence of SWNTs was confirmed by Raman spectroscopy and transmission electron microscopy. SWNTs produced in this way should provide economic benefits and also contribute to a cleaner environment.

Computer Simulation of Core Structure of Screw Dislocations in C60 Crystals Using Girifalco Potential.

The equilibrium molecular configuration around a 1/2[101] screw dislocation in C60 crystals in a fcc phase was calculated by means of molecular dynamics. The molecules were assumed to be rigid and the spherical intermolecular potential derived by Girifalco was utilized. The dislocation was found to dissociate into two Shockley partials. The partial dislocation had a spreadout core and the width of the Burgers vector density at the half-peak height reached 13 times the magnitude of the Burgers vector.

Systematics of Hyperfine Fields at Impurity Nuclei in Ferromagnetic Rare Earth Compounds GdZn and GdCd.

The hyperfine (hf) fields at the nuclei of N, Ge, Tl, V and Fe impurities in ferromagnetic GdZn and GdCd have been measured by NMR and Mossbauer methods. The results, together with the reported ones, nearly complete the systematics of the hf fields at s p and 3 d impurities in GdZn(Cd). The hf fields at 4 s p , 5 s p and 6 s p impurities are always negative, exhibiting a similar variation with increasing the impurity valence. The trend of the hf fields at 3 d impurities shows local moment contributions to the hf field at the middle of the 3 d series, indicating finite local moments on Mn and Fe impurities. These results are found to resemble the systematics of the hf fields at impurities in Gd and are qualitatively explained by the theory of the hf field developed for Fe and Ni hosts.