共查询到18条相似文献,搜索用时 250 毫秒
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用12kW转靶X射线衍射装置测定了非晶半导体a-As2Se3,a-AsSe以及a-As0.05,Se0.95的k吸收EXAFS,a-As2Se3经T≤Tg(玻璃转变温度)的不同温度处理后,亦进行了测定。由获得的径向结构函数分析表明:尽管a-As2Se3的短程结构与晶态c-As2Se3十分相似,但经过低于Tg的退火处理后,其径向结构函数发生了一定的变化。熔态淬火制备的a-As2Se3块体亦发生结构弛豫。此外,在非晶态As-Se二元系中随As含量的变化,材料的近程结构亦不同。
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用转靶X射线源及弯晶EXAFS谱仪测定了Fe80B20及Fe80Si6B14金属玻璃中铁的X射线K吸收谱。由EXAFS谱确定了两种金属玻璃的近邻结构参量。此外,通过测定XANES谱并与纯铁及其有关的化合物Fe2B,FeB中铁的XANES比较发现:吸收边能量、“白线”结构等均出现一些变化,表明两种金属玻璃的近邻原子Fe-B,Fe-Si以及Fe-Fe之间的相互作用比铁与硼所形成的稳定化合物中要强,这对于决定金属玻璃的短程序结构具有重要的作用。
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本工作用X射线散射技术研究了金属一类金属玻璃合金Pd77Si16.5Ag6.59,Co42.9Ni27.3Fe7.8Si8B14和Co50.7Ni19.5Fe7.8Si6B16的结构。求出了它们的干涉函数I(s)和原子径向分布函数RDF(r),并由此获得了有关结构信息的原子平均距离、最近邻配位数和短程有序畴半径。此外,对这些合金的RDF(r)第一峰作了高斯分布拟合,求得了比较好的拟合方程,并用近似方法估算了其中金属-金属原子间的配位数。
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结合径向基函数方法有效地提高了两个全局模型预言原子核电荷半径的精度和能力。利用885个原子核电荷半径实验数据进行留一交叉验证,Skyrme Hartree-Fock-Bogoliubov(HFB25)模型的计算结果与实验测量结果的均方根偏差从0.025 fm降到了0.018 fm,基于Weizs?cker-Skyrme(WS*)核质量模型给出的壳修正能和形变参数提出的四参数公式的计算结果与实验测量结果的均方根偏差从0.022 fm降到了0.017 fm。两个模型结合径向基函数方法预言最新的144个实验值的均方根偏差仅为0.015 fm。通过研究径向基函数方法对HFB25和WS*两个模型在超重区域预言值的修正程度发现,径向基函数方法对于WS*模型在超重区域的修正值大部分可以保持在0.1 fm以内,而对于HFB25模型在超重区域的修正值大部分都超过了0.1 fm,这对于分析模型误差以及进一步改善原子核电荷半径的预言精度非常有用。 相似文献
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J.P. Carini Soumen Basak S.R. Nagel B.C. Giessen Ching-Long Tsai 《Physics letters. A》1981,81(9):525-526
We report the first measurement of the thermoelectric power Q, of a metallic glass that contains only normal metals. The thermoelectric power of amorphous Ca0.8Al0.2 has been measured as a function of temperature from 10 K to 420 K. It is found that Q is positive, varies linearly with temperature and has a small slope. This is similar to the thermoelectric power found for other metallic glasses containing large concentrations of transition metal atoms. 相似文献
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C. J. Robinson M. G. Samant E. E. Marinero 《Applied Physics A: Materials Science & Processing》1989,49(6):619-629
The atomic structure of amorphous Tb20Fe80 thin films has been studied by Extended X-ray Absorption Fine Structure (EXAFS) of both FeK and TbL
III absorption edges. The local site geometry around Fe atoms shows predominantly Fe nearest neighbors with an Fe-Fe distance distribution centered on 2.50±0.02 Å and a coordination number of 9.1±1. In contrast, the radial structure function (RSF) obtained at the Tb edge is broad and asymmetric. The peak in the RSF corresponds to a Tb-Fe near neighbor distance of 2.94±0.1 Å with no evidence for Tb-Tb nearest neighbor coordination. The width and the shape of the RSF suggest that the Tb-Fe atomic environment is anisotropic and strained probably as a consequence of the growth process. This distorted atomic environment is suggested to be responsible for the magnetic anisotropy in these alloys. Thermal annealing at 200 °C leads to reduction inK
u. We propose that this results from reordering of the Tb local environment such that the average structural anisotropy in the distribution is reduced. EXAFS data show that annealing at 400°C causes precipitation of bcc polycrystalline Fe. The addition of 7 at.% Au to the alloy prevents this recrystallization and preserves the amorphous state but does not prevent the structural relaxation which reducesK
u at lower temperatures. 相似文献
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Extended X-ray absorption fine structure (EXAFS) and molecular dynamic (MD) simulation were used to study the short-range order in Zr2Ni amorphous alloy. It is found that the bond length is significantly shorter for unlike atoms but longer for like atoms in amorphous state than that in the crystalline state. Meanwhile, the coordination number of Ni atom in amorphous structure is only half of that in ideal Zr2Ni crystalline. Based on these results, we proposed that there exists Zr2Ni-like chemical short-range order in the Zr2Ni amorphous alloy. 相似文献
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F. Evangelisti M.G. Proietti A. Balzarotti F. Comin L. Incoccia S. Mobilio 《Solid State Communications》1981,37(5):413-416
The structure of a-Ge as a function of the deposition temperature Ts has been studied by the EXAFS technique for the first time. The results demonstrate the sensitivity of EXAFS to structural differences in the medium range. The data provide strong evidence for a continuous transition from the amorphous to the crystalline phase over a temperature interval form 130°C to 300°C. The analysis of the data is in line with the microcrystal model of amorphous Ge films and allows an estimate of the average grain size for the lower range Ts used. 相似文献
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ABSTRACTIn this work, we use extended X-ray absorption fine structure (EXAFS) data collected using nano-polycrystalline diamond anvil cell to study the atomic arrangement in Zr–Cu metallic glass in high pressure (HP) conditions. To reveal the microscopic details of stress accommodation mechanism, we performed molecular dynamics (MD) simulations of the HP atomic arrangement. By comparing the experimental and the calculated Zr and Cu K-edge EXAFS signal we prove the realistic character of the computer simulations. A detailed geometrical analysis of the simulated atomic configurations shows that with increasing hydrostatic pressure the local structure of Zr–Cu amorphous alloy becomes gradually dominated by Cu-centred icosahedral structural motifs involving fivefold symmetry incompatible with crystalline ordering. The variation of the short-range order is attributed to preferential straining of mechanically soft bonds between zirconium atoms. 相似文献
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X-ray diffraction patterns have been obtained from Cu57 — Zr43 alloy in both amorphous and liquid states. After calculating the structure factor by means of the common Fourier analysis, the atomic radial distribution function was evaluated from which interatomic distance and coordination number were obtained. In the essential feature of the structure factor in the amorphous state was quite similar to that in the liquid state. There is a good agreement between the structure factor determined in this work and that calculated on the basis of the hard sphere mixture model except for the presence of the splitting of a second peak maximum in the former. These results suggest that the atoms in the nearest neighbour distance in the amorphous state consist mainly of the disorderly distributed atoms as those in the liquid state. But a deformed crystalline-like arrangement of atoms as those in a hcp or fcc structure contributes partly to the short range order in the amorphous state. 相似文献