1991 Fiscal Year Final Research Report Summary
The semiconductor-metal transition and the structural change in fluid selenium near the liquid-gas critical point.
| Project/Area Number |
02452042
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | Hiroshima University |
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Principal Investigator |
TAMURA Kozaburo Hiroshima University, Faculty of Integrated Arts and Sciences, Professor, 総合科学部, 教授 (30155262)
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| Co-Investigator(Kenkyū-buntansha) |
WATABE Mitsuo Hiroshima University, Faculty of Integrated Arts and Sciences, Professor, 総合科学部, 教授 (20004286)
HOSOKAWA shinya Hiroshima University, Faculty of Integrated Arts and Sciences, Research Associat, 総合科学部, 助手 (30183601)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Liquid semiconductor / Metal-nonmetal Transition / Liquid-gas Critical Point / High Temperature and Pressure / X-ray Diffraction / Selenium / Expanded Metal |
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| Research Abstract |
In order to clarify the mechanism of the semiconductor-metal transition in fluid Se which occurs near the liquid-gas critical point (critical data of Se ; T_c= 1590ﾟC, P_c= 380 bar, d_c= 1.85 g/cm^3) , we have performed X-ray diffraction measurements for fluid Se in the temperature and pressure range up to 1500ﾟC and 815 bar. We have developed a new type of high-pressure vessel and a new sample cell made of single-sapphire of our own design. For the X-ray diffraction measurements at high temperatures and pressures we have adopted an energy-dispersive method.
We have obtained the structure factor and the pair distribution function as functions of temperature and pressure. From the detailed analysis of the pair distribution function we conclude that the twofold coordinated structure is largely preserved in the region where the optical gap disappears and the progressive increase of conductivity becomes evident. This contrasts with the conventional theory that the semiconductor-metal transition is induced by the structural change from the twofold to threefold coordinated structure. On the basis of these findings we speculate on the existence of the small chain molecule with planer zigzag conformation which may cause the transition to the metallic state in fluid Se.
In addition, we have applied our experimental technique to the measurements for expanded fluid Hg on which no structural studies have been made so far. We have measured X-ray diffraction for fluid Hg in the density range from 13.55 to 6.8 g/cm^3.
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