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The atomic and electronic structure of liquidN-methylformamide as determined from diffraction experiments

 

作者: J. Neuefeind,   M.D. Zeidler,   H.F. Poulsen,  

 

期刊: Molecular Physics  (Taylor Available online 1996)
卷期: Volume 87, issue 1  

页码: 189-201

 

ISSN:0026-8976

 

年代: 1996

 

DOI:10.1080/00268979600100101

 

出版商: Taylor & Francis Group

 

数据来源: Taylor

 

摘要:

The structure of liquidN-methylformamide (NMF) has been investigated using synchrotron radiation at 77 keV and 95 keV. The use of high energy photons has several advantages, in this case in particular 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 Å-1<Q< 24·0 Å-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 intra-molecular 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, there is comment on whether the different interaction mechanisms of neutrons and photons can be used to access directly 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.

 

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