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2003 Fiscal Year Final Research Report Summary

Pressure-induced amorphous-amorphous phase transition in molecular solids with tetrahedral molecules

Research Project

Project/Area Number 14540296
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field 固体物性Ⅰ(光物性・半導体・誘電体)
Research InstitutionOchanomizu University

Principal Investigator

HAMAYA Nozomu  Ochanomizu Univ., Graduate School of Humanities and Sciences, Professor, 大学院・人間文化研究科, 教授 (70156420)

Project Period (FY) 2002 – 2003
Keywordsmolecular solid / pressure-induced amorphization / pressure-induced molecular dissociation / amorphous structure analysis / amorphous-amorphous phase transition / synchrotron radiation / high-pressure x-ray diffraction
Research Abstract

When the high-pressure amorphous state induced by compression of molecular crystal SnI_4 is decompressed from 30 GPa, a discontinuous shift of the position of the first diffraction peak occurs at 3 GPa. Subsequent compression yields the shift in the reverse direction at 6 GPa. These previous observations suggest an occurrence of structural change in the amorphous state. The objective of the present work is to study change of amorphous structure quantitatively and to obtain knowledge of phase transition in a disordered state.
We first carried out synchrotron radiation x-ray measurements and studied amorphous structure near the amorphous-amorphous phase transition. The position, width and shape of the first peak in the structure factor, S(Q), were confirmed to change discontinuously at 3 GPa. The reduced radial distribution function G(r) was obtained from Fourier transform of S(Q) at each pressure. Examination of G(r) showed that the distances corresponding to the one between the Sn and I … More ions and the I ions within the tetrahedral molecule are missing in G(r) above 3 GPa, while below 3 GPa distinct peaks appearing at these intramolecular atomic distances clearly indicate the formation of the tetrahedral molecules in the low-pressure amorphous state. Upon the second compression the reverse process took place at 7 GPa with a large pressure-hysteresis. Those observations suggest that the structural change in pressure-induced amorphous SnI_4 is of first-order phase transition. A characteristic of the amorphous-amorphous phase transition in SnI_4 is that the formation/dissociation of the tetrahedral molecules occurs. In this respect this phase transition has a stronger similarity with that in liquid phosphor at high pressure and high temperature rather than the pressure-induced low density-high density transition in amorphous ice.
The density of amorphous solid has been a physical parameter difficult to measure under pressure. We demonstrated that the density can be obtained from G(r) with precision high enough to distinguish the difference between the low and high pressure amorphous states. We showed that the amorphous-amorphous phase transition in SnI_4 is accompanied by a pressure-hysteresis of the density and by an anomalous hardening above the transition pressure upon decompression. Our recent Raman spectroscopic measurements showed that a new vibration mode is produced at the transformation form the high-pressure to the low-pressure amorphous state.
Part of the results of this study was presented at the 19th IUCr Congress of General Assembly (Geneva) in Aug., 2002 and the 19^<th> International Conf.on High Pressure Sci.and Technology (Bordeaux) in July, 2003. Less

  • Research Products

    (14 results)

All Other

All Publications (14 results)

  • [Publications] A.Ohmura, N.Hamaya, K.Sato, C.Ogawa, M.Isshiki, Y.Ohishi: "Structure analysis of high-pressure amorphous phase of SnI_4"J.Phys. : Cond.Matt.. 14. 10553-10556 (2002)

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      「研究成果報告書概要(和文)」より
  • [Publications] A.Ohmura, K.Sato, H.Yamazaki, N.Hamaya, M.Isshiki, Y.Ohishi: "Pressure-induced amorphous-amorphous transition in molecular solid SnI_4"Acta Crystallog.. A58 Supplement. C178 (2002)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Sekiya, M.Okumura, S.Kurita, N.Hamaya: "Pressure-induced phase transformation within anatase titanium dioxide"High Press.Res.. 23. 333-338 (2003)

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      「研究成果報告書概要(和文)」より
  • [Publications] W.Utsumi, F.Okada, T.Taniguchi, K.Funakoshi, T.Kikegawa, N.Hamaya, O.Shimomura: "In situ x-ray diffraction of graphite-diamond transformation using various catalysts under high pressures and high temperatures"J.Physics : Condensed Matter. 16. S1017-S1026 (2004)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Okada, W.Utsumi, H.Kaneko, V.Turkevich, N.Hamaya, O.Shimomura: "Kinetics of the graphite-diamond transformation in aqueous fluid determined by in-situ X-ray diffractions at high pressures and temperatures"Phys.Chem.Minerals. 31. 261-268 (2004)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] K.Fuchizaki, Y.Fujii, Y.Ohishi, A.Ohmura, N.Hamaya, Y.Katayama: "Determination of low-pressure crystalline-liquid phase boundary of SnI_4"J.Chem.Phys.. (in press). (2004)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 浜谷望: "実験化学講座 第6巻「温度・熱,圧力:11.2.3 高圧下での測定 X線回折・分光法」"丸善(印刷中).

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] A.Ohmura, N.Hamaya, K.Sato, C.Ogawa, M.Isshiki, Y.Ohishi: "Structure analysis of high-pressure amorphous phase of SnI_4"J.Phys. : Cond.Matt. 14. 10553-10556 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] A.Ohmura, K.Sato, H.Yamazaki, N.Hamaya, M.Isshiki, Y.Ohishi: "Pressure-induced amorphous-amorphous transition in molecular solid SnI_4"Acta Crystallog.A. 58 Supplement. C178 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] T.Sekiya, M.Okumura, S.Kurita, N.Hamaya: "Pressure-indudec phase transformation within anatase titanium dioxide"High Press.Res.. 23. 333-338 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] W.Utsumi, T.Okada, T.Taniguchi, K.Funakoshi, T.Kikegawa, N.Hamaya, O.Shimomura: "In situ x-ray diffraction of graphite-diamond transformation using various catalysts under high pressures and high temperatures"J.Physics : Condensed Matter. 16. S1017-S1026 (2004)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] T.Okada, W.Utsumi, H.Kaneko, V.Turkevich, N.Hamaya, O.Shimomura: "Kinetics of the graphite-diamond transformation in aqueous fluid determined in-situ X-ray diffractions at high pressures and temperatures"Phys.Chem.Minerals. 31. 261-268 (2004)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Fuchizaki, Y.Fujii, Y.Ohishi, A.Ohmura, N.Hamaya, Y.Katayama, T.Okada, W.Ustumi: "Determination of low-pressure crystalline-liquid phase boundary of SnI_4"J.Chem.Phys.. (in press).

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] N.Hamaya: "Temperature-Heat and Pressure : X-ray Diffraction and Spectroscopy Measurements at High Pressure"Experimental Chemistry Series(in Japanese). Vol.6 Chapter 11.2.3(in press).

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      「研究成果報告書概要(欧文)」より

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Published: 2005-04-19  

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