MICROSCOPIC ORIGIN OF THE PHASE TRANSITION IN LIQUID CHALCOGENS

液态硫族元素相变的微观起源

基本信息

项目摘要

It is known that the liquid chalcogens such as Te and Se undergo the liquid-liquid phase transition at high temperature. This structural transition is accompanied by the semiconductor-metal (S-M) transition.The main purpose of the present project is to elucidate the microscopic origin of the phase transition observed for the liquid chalcogen. A consistent analysis of g(r) for liquid (1-) As-Te mixtures obtained from the neutron diffraction (ND) measurements has been performed by Hoshino, Maruyama and Endo taking the structural information on the extended X-ray absorption fine structure (EXAFS) data into consideration. Our important findings are that in the 1-As-Te mixtures the change of As sites from the threefold coordinated to twofold coordinated configuration is associated with the metallization at high temperature and the S-M transition observed for 1-As-Te mixtures arises from the transformation to densely packed configuration composed of shortened chain- molecules which is caused … More by volume contraction.Yao et al. have measured the sound attenuation in 1-Te_<50>, Se_<50> in a wide temperature and pressure range and found a sharp absorption peak near the S-M transition, which may be interpreted as a resonance relaxation originating from the inter-chain oscillating motion.The computer simulation study is indispensable for obtaining information on the microscopic mechanism of the transition. Oda and Hiwatari have carried out an ab initio molecular dynamics simulation of 1-oxygen, a molecular fluid in which the individual O_2 units carry a molecular magnetic moment. The atomic structure shows a strong preference for parallel alignment of the first neighbor molecules. The magnetic structure shows strong short range antiferromagnetic correlations.Kimura has studied the nematic-isotropic phase transition in the liquid crystalline mixtures of rod-like and disk-like molecules by a mean field theory. The thermotropic phase transition have been found from the isotropic to one of the two types of uniaxially symmetric nematic phases; optically positive N and negative N. Less
已知液态硫属元素如Te和Se在高温下经历液-液相转变。这种结构转变伴随着硫族元素-金属(S-M)的相变。本项目的主要目的是阐明所观察到的液态硫族元素相变的微观起源。Hoshino,Maruyama和Endo利用扩展X射线吸收精细结构(EXAFS)数据对液态(1-)As-Te混合物的g(r)进行了一致性分析。我们的重要发现是,在1-As-Te混合物中,As位从三配位到二配位的转变与高温金属化有关,而1-As-Te混合物中观察到的S-M转变则是由短链分子向密集堆积构型的转变引起的 ...更多信息 Yao等测量了1-Te_<50>2,Se_2<50>在宽温压范围内的声衰减,发现在S-M跃迁附近有一个尖锐的吸收峰,这可能是由链间振荡运动引起的共振弛豫,计算机模拟研究对于获得跃迁的微观机制是必不可少的。Oda和Hiwatari对1-氧进行了从头算分子动力学模拟。原子结构显示出强烈的偏好平行排列的第一邻居分子。Kimura用平均场理论研究了棒状和盘状分子混合液晶的向列-各向同性相变。已经发现从各向同性到两种类型的单轴对称双相之一的热致相变:光学正N和光学负N。少

项目成果

期刊论文数量(25)
专著数量(0)
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会议论文数量(0)
专利数量(0)
K. Maruyama: "Neutron diffraction of liquid arsenic-tellurium mixtures near the semiconductor-metal transition"J. Non-cryst. Solids. 312-314. 356-360 (2002)
K. Maruyama:“半导体-金属过渡附近液态砷-碲混合物的中子衍射”J。
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H. Endo: "Local structure of liquid Te studied by neutron diffraction and EXAFS"Z. Phys. Chem.. in press.
H. Endo:“通过中子衍射和 EXAFS 研究液体 Te 的局域结构”Z。
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K.Maruyama: "Neutron Diffraction of Liquid Arsenic-Tellurium Mixtures near Semiconductor-Metal Transition"J. Non-Cryst. Solids. (in press). (2002)
K.Maruyama:“半导体-金属转变附近液态砷-碲混合物的中子衍射”J。
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A.Baumketner: "Finite-Size Dependence of the Bridge-Function Extracted from Molecular Dynamics Simulations"Phys. Rev.. E63. 61201-61204 (2001)
A.Baumketner:“从分子动力学模拟中提取的桥函数的有限尺寸依赖性”Phys。
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H.Hoshino: "The network-chain transformation in the liquid As-Te mixtures near the semiconductor-metal transition"Z.Phys.Chem.. (in press).
H.Hoshino:“半导体-金属转变附近液体 As-Te 混合物中的网络链转变”Z.Phys.Chem..(出版中)。
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ENDO Hirohisa其他文献

ENDO Hirohisa的其他文献

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{{ truncateString('ENDO Hirohisa', 18)}}的其他基金

Structural and Semiconductor-Metal Transition in liquid Se
液态硒中的结构和半导体-金属转变
  • 批准号:
    10640356
  • 财政年份:
    1998
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for Scientific Research (C)
Electronic and Structural Properties of the Isolated Chains Confined in the Pores of Mordenite.
丝光沸石孔隙中限制的孤立链的电子和结构特性。
  • 批准号:
    60420010
  • 财政年份:
    1985
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for General Scientific Research (A)

相似海外基金

The void and meso-scale structure in the liquid chalcogens
液态硫属元素中的空隙和细观结构
  • 批准号:
    20540366
  • 财政年份:
    2008
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for Scientific Research (C)
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