Neutron diffraction, determination structure

Ellison RD, Johnson CK, Levy HA (1971) Glycolic acid direct neutron diffraction determination of crystal structure and thermal motion analysis. Acta Cryst B 27 333-344... 

Koetzle. T.F. Lehmann, M.S. Hamilton. W.C. Precision neutron diffraction determination of protein and nucleic acid components. IX. The crystal and molecular structure of 4-hydroxy-L-proline. Acta Crystallogr.. B 1973. 29. 

Harrison, W.TA., Hegwood, S.L., and Jacobson, A.J. (1995) A powder neutron diffraction determination of the structure of SrgCosOis, formerly described as the low-temperature hexagonal form of SrCo03. J. Chem. Soc., Chem. 

The oxygen atoms in rhombohedral PbO have proved impossible to locate by X-ray intensity measurements, but their positions were determined by neutron diffraction. The structure consists of a chain in which lead has two nearest oxygen neighbours (Pb-0 = 2 21 A). These chains are loosely bonded into layers by two Pb-O bonds (Pb-0 = 2 49 A). 

Neutron diffraction determines nuclear coordinates whereas X-ray diffraction refers to maxima of the electron density distribution. A systematic investigation of the differences in bond lengths from X-ray and neutron diffraction analyses of the same crystal structure gave significant differences for dx-dn for C-H and O-H bonds, respectively —0.096(7) and -0.155(10) A (26). This is the reason why the X-ray X-H bond lengths have to be normalized to standard, neutron diffraction, values for the interpretation of hydrogen bonding in molecular crystals. 

As with other diffraction techniques (X-ray and electron), neutron diffraction is a nondestructive technique that can be used to determine the positions of atoms in crystalline materials. Other uses are phase identification and quantitation, residual stress measurements, and average particle-size estimations for crystalline materials. Since neutrons possess a magnetic moment, neutron diffraction is sensitive to the ordering of magnetically active atoms. It differs from many site-specific analyses, such as nuclear magnetic resonance, vibrational, and X-ray absorption spectroscopies, in that neutron diffraction provides detailed structural information averaged over thousands of A. It will be seen that the major differences between neutron diffraction and other diffiaction techniques, namely the extraordinarily... 

On an industrial scale PCI3 is sprayed into steam at 190 and the product sparged of residual water and HCl using nitrogen at 165. Phosphorous acid forms colourless, deliquescent crystals, mp 70. T, in which the structural units shown form four essentially linear H bonds (O - H 155-I60pm) which. stabilize a complex 3D network. The molecular dimensions were determined by low-temperature single-crystal neutron diffraction at 15K.f - ... 

Definitive proof of the structure of porphine in the solid state awaits a variable-temperature crystallographic (X-ray or neutron diffraction) study the analysis of the anisotropic displacement factors (ADP) should disclose any rotational motion or its absence as well as determine the positions of the inner hydrogens. A search in the September 1998 version of the Cambridge Structural Database [CSD (91MI187)] showed that the only structures of porphine (codename PORPIN) were obtained in 1965 and 1972. 

Bowron et al. [11] have performed neutron diffraction experiments on 1,3-dimethylimidazolium chloride ([MMIM]C1) in order to model the imidazolium room-temperature ionic liquids. The total structure factors, E(Q), for five 1,3-dimethylimidazolium chloride melts - fully probated, fully deuterated, a 1 1 fully deuterated/fully probated mixture, ring deuterated only, and side chain deuterated only - were measured. Figure 4.1-4 shows the probability distribution of chloride around a central imidazolium cation as determined by modeling of the neutron data. 

The definitive structural determination of the P -hydroxide is the powder neutron diffraction work of Greaves and Thomas on / - Ni(OD)2 [22], They did neutron... 

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