The Atomic and Electronic Structure of Liquid N- Methylformamide as Determined from Diffraction Experiments
The Atomic and Electronic Structure of Liquid N- Methylformamide as Determined from Diffraction Experiments
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衍射实验测定液体 N-甲基甲酰胺的原子和电子结构
DOI：
10.1080/00268979600100101
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
H. Poulsen
中科院分区：
文献类型：
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作者：
J. Neuefeind;M. Zeidler;H. Poulsen
用同步辐射研究了液态N-甲基甲酰胺（NMF）的结构。使用高能光子有几个优点，在这种情况下，特别是大的可达动量转移范围，低吸收和直接与中子衍射的可比性。动量传递的范围为0.6 \AA$^{-1} <$ Q $<$24.0 \AA$^{-1}$。在相同的动量转移范围内的相同样品的中子衍射数据已经公布。在该研究中，研究了两种不同同位素取代的物质。为了比较中子和光子衍射数据正确的反向蒙特卡罗（RMC-）模拟已经进行。必须对标准RMC代码进行一些修改，从而对分子间和分子内距离引入不同的约束，因为这些距离在液体NMF中部分重叠。RMC-模拟只有中子数据作为输入进行，以测试X射线数据的质量。从RMC-配置计算的光子结构因子被认为是同意与目前的实验数据，而它大大偏离早期的X射线工作，使用低能量光子（17千电子伏）。最后，我们讨论了中子和光子的不同相互作用机制是否可以用来直接访问液体中的电子结构。证据是液体NMF的弹性自散射部分相对于独立原子近似的变化。这种变化可以用一个简单的带电原子模型来解释。
The structure of liquid N-methylformamide (NMF) has been investigated using synchrotron radiation at 77 and 95 keV. The use of high energy photons has several advantages, in this case especially the large accessible momentum transfer range, the low absorption and the direct comparability with neutron diffraction. The range of momentum transfer covered is 0.6 \AA$^{-1} <$ Q $<$24.0 \AA$^{-1}$. Neutron diffraction data on the same sample in the same momentum transfer range have been published previously. In that study two differently isotope - substituted species were investigated. In order to compare neutron and photon diffraction data properly Reverse Monte Carlo (RMC-) simulations have been performed. Some modifications had to be added to the standard RMC- code introducing different constraints for inter- and intramolecular distances as these distances partly overlap in liquid NMF. RMC- simulations having only the neutron data as input were carried out in order to test the quality of the X-ray data. The photon structure factor calculated from the RMC- configurations is found to agree well with the present experimental data, while it deviates considerably from earlier X-ray work using low energy photons (17 keV). Finally we discuss whether the different interaction mechanisms of neutrons and photons can be used to directly access the electronic structure in the liquid. Evidence is presented that the elastic self scattering part of liquid NMF is changed with respect to the independent atom approximation. This modification can be accounted for by a simple charged atoms model.
Y.Aoki.：Theochem。
DOI：
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发表时间：
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期刊：
影响因子：
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作者：
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