Neutron diffraction, determination

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... 

In elongated H2 complexes, experimental and computational studies indicate that the 7 -H2 ligand is greatly delocalized and caimot be envisaged as a fixed, rigid unit [7]. Rapid motion of two hydrogen atoms occurs on a flat potential energy surface with a shallow minimum at the neutron-diffraction determined position of 1.2 A for trans-[OsCl(H2)(dppe)2]+. 

In order to meet the needs of scientists working on modem aspects of stmctural molecular science, such as supramo-lecular chemistry, the instrumentation used for neutron diffraction determinations has developed enormously over the last few years. This was an essential advance, because neutron diffraction is intrinsically a flux-limited technique, due to the relatively low neutron fluxes available from even the most advanced sources. For the stmctural determination of a sample under a set of variable conditions, experiment times of a few hours per determination are becoming the norm. This also allows for the screening of larger numbers of different materials, further increasing the power of the technique in this area. 

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. 

Kea74] Keating, D.T. and LaPlaca, S.J., Neutron Diffraction Determination of the Number and Displacement of the At-... 

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. 

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