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Fuchizaki, Kazuhiro*; Hamaya, Nozomu*; Katayama, Yoshinori
Journal of the Physical Society of Japan, 82(3), p.033003_1 - 033003_4, 2013/03
Times Cited Count：12 Percentile：60.45(Physics, Multidisciplinary)An in situ synchrotron X-ray absorption measurement was carried out to estimate the density of liquid SnI. The characteristic densities of the low- and high-pressure liquids were found to be 4.6-4.7 and 4.9-5.0 g/cm
, respectively, and their region is separated at around 1.7 GPa. The difference in density, although a slight amount of 0.3-0.4 g/cm, strongly suggests the existence of a weak but discontinuous phase transition at that pressure between the two liquid regions.
Fuchizaki, Kazuhiro*; Hamaya, Nozomu*; Hase, Takaki*; Katayama, Yoshinori
Journal of Chemical Physics, 135(9), p.091101_1 - 091101_4, 2011/09
Times Cited Count：14 Percentile：44.71(Chemistry, Physical)We have shown from in situ synchrotron X-ray diffraction measurements that there are two thermodynamically stable liquid forms of SnI, depending on the pressure. Based on the liquid-liquid critical point scenario, our recent measurements suggest that the second critical point, if it exists, may be located in a region close to the point at which the melting curve of the crystalline phase abruptly breaks. This region is, unlike that of water, experimentally accessible with relative ease.
Fuchizaki, Kazuhiro*; Hase, Takaki*; Yamada, Akihiro*; Hamaya, Nozomu*; Katayama, Yoshinori; Funakoshi, Kenichi*
Journal of Chemical Physics, 130(12), p.121101_1 - 121101_4, 2009/03
Times Cited Count：20 Percentile：57.42(Chemistry, Physical)In situ synchrotron X-ray diffraction measurements on tin tetraiodide, which consists of SnI tetrahedral molecules at ambient pressure, have been performed. It was established that the liquid forms existing above and below 1.5 GPa, where the slope of the melting curve of the solid phase changes abruptly, have different structures. This discovery offers evidence of thermodynamically stable polyamorphism in general compounds as well as in elements. A possible phase diagram that includes the two amorphous states already found is proposed based on the pseudobinary regular solution model. The vertex-to-face orientation between the nearest molecules plays a key role in the transition from the low-pressure to the high-pressure liquid phase.
Fuchizaki, Kazuhiro*; Fujii, Yasuhiko*; Oishi, Yasuo*; Omura, Ayako*; Hamaya, Nozomu*; Katayama, Yoshinori; Okada, Taku
Journal of Chemical Physics, 120(23), p.11196 - 11199, 2004/06
Times Cited Count：22 Percentile：58.21(Chemistry, Physical)The location of the liquidus in the low-pressure crystalline phase of SnI was determined utilizing 
X-ray diffraction measurements under pressures up to approximately 
GPa. The liquidus is not well fitted to a monotonically increasing curve such as Simon's equation, but breaks near 
GPa and then becomes almost flat. The results are compared to those from molecular dynamics simulations. Ways to improve the model potential adopted in the simulations are discussed.
Okada, Taku; Utsumi, Wataru; Kaneko, Hiroshi*; Turkevich, V.*; Hamaya, Nozomu; Shimomura, Osamu*
Physics and Chemistry of Minerals, 31(4), p.261 - 268, 2004/05
Times Cited Count：12 Percentile：41.33(Materials Science, Multidisciplinary)The graphite-diamond transformation was investigated by in situ time-resolved X-ray diffraction experiments using aqueous fluid containing dissolved MgO as the diamond forming catalyst under conditions of 6.6-8.9 GPa and 1400-1835 
C. The transformed volume fractions of diamond as a function of time under various pressure-temperature conditions were obtained and analyzed using the JMAK rate equation. Variations in the nucleation and growth processes during diamond formation as a function of pressure and temperature were clarified.
X-ray diffraction of graphite-diamond transformation using various catalysts under high pressures and high temperaturesUtsumi, Wataru; Okada, Taku; Taniguchi, Takashi*; Funakoshi, Kenichi*; Kikegawa, Takumi*; Hamaya, Nozomu; Shimomura, Osamu
Journal of Physics; Condensed Matter, 16(14), p.S1017 - S1026, 2004/04
Times Cited Count：14 Percentile：54(Physics, Condensed Matter)The graphite-diamond transformation was investigated using in-situ time-resolved X-ray diffraction experiments with a MgO dissolved aqueous fluid as the diamond forming catalyst under conditions of 6.6-8.8 GPa and 1400-1835C. Experiments were conducted using a 180-ton DIA-type cubic-anvil apparatus installed on the beamline BL14B1 at SPring-8, a third-generation synchrotron radiation facility in Japan. By analyzing the kinetic data using the JMAK rate equation, it was clarified that altering the pressure-temperature conditions drastically changes the nucleation and growth process of diamond.
Hamaya, Nozomu; Watanuki, Tetsu
Nihon Kessho Gakkai-Shi, 42(1), p.51 - 58, 2000/02
no abstracts in English
Konishi, Hiroyuki; Fujii, Yasuhiko*; Hamaya, Nozomu*; *; *; *; L.Wu*; *; *; *
Review of Scientific Instruments, 63(1), p.1035 - 1038, 1992/01
Times Cited Count：7 Percentile：60.99(Instruments & Instrumentation)no abstracts in English
Fuchizaki, Kazuhiro*; Sakagami, Takahiro*; Miyauchi, Arata*; Hamaya, Nozomu*; Hattori, Takanori; Katayama, Yoshinori
no journal, ,
The results of the synchrotron X-ray diffraction on liquid SnI revealed the following characteristics on the phase transformation between low- and high-density liquids. (1) The local structure continuously changes with pressure. (2) The density shows no systematic change with pressure. The first one is confirmed by the continous pressure-induced change of off-tetragonalinity in the local structure. On the other hand, the second statement is still less convincible because it based on the indirect method to measure liquid density. To confirm the second statement, the direct measurement of the liquid density is necessary. For that purpose, we determined density from X-ray absorption of liquid sample. The results showed that the liquid density slightly jumps by the amount of 0.3 g/cc at 1.5 GPa, where the PT-melting curve shows a knick. Now we are trying to reveal the details based on more accurate data.
