Neutron studies

Schweizer, J. and Tasset, F. (1980) Polarised neutron study of the RCo5 intermetallic compounds ... 

Zheludev, A., Bonnet, Luneau, D. et al. (1995) The spin density in an imino nitroxide free radical a polarized-neutron study, Physica B, 213-214, 268-271. 

Kennedy, S.J., Brown P.J. and Coles, B.R. (1993) A polarised neutron study ofthe magnetic form factors in CeFe2, J. Phys. Cond. Mat., 5(29), 5169-5178. 

X-ray and neutron studies of os-enol systems at liquid helium temperatures... 

Fig. 16 The migration of the proton along an O-H- - O bond in a co-crystal urea-phosphoric acid (1 1), as the temperature is increased from 150 K (top) to 335 K (bottom), becoming essentially centred (neutron study) [55]... 

The atomic dipole moment can be attributed to the preferential population of specific nonspherical atomic orbitals. In particular, this is the case for atoms with doubly-filled nonbonding lone-pair orbitals, such as the oxygen atoms in C—O—H and H—O—H, or oxygen in a terminal position as it is in the carbonyl group. An early demonstration of the bias introduced in X-ray positions of non-hydrogen atoms was the combined X-ray and neutron study of oxalic acid dihydrate (Coppens et al. 1969), which showed the X-ray positions of the oxygen atoms to be systematically displaced by small amounts into the direction of the lone pair density. 

A complex with an Fe—Fe bond for which the electron density is available is bis(dicarbonyl-7i-cyclopentadienyl iron), [C5H5Fe(CO)2]2 (Fig. 10.13) (Mitschler et al. 1978). The 18-electron rule again requires only a single bond to explain the observed diamagnetism. The combined X-ray and neutron study indicates a complete absence of density accumulation in the metal-metal bonding region of the standard deformation density, in agreement with an SCF theoretical density,... 

As with neutron powder methods, both monochromatic and time-of-flight (Laue) techniques have been used for single-crystal neutron studies. Such studies are much less numerous, however, as a result of the difficulty of compressing suitably sized (>1 mm ) single-crystal sample to the required pressure while maintaining the crystal quality. The piston cylinder cell design of Me Whan and others [128] has been used at the ILL reactor source for a number of neutron structural studies to... 

Note that because of the different scattering mechanisms, the bond lengths determined by X-ray and neutron studies will be different. The neutron determination will give the true distance between the nuclei, whereas the X-ray values are distorted by the size of the electron cloud and so are shorter. 

Bouquiere, J. P., Finney, J. L., Lehmann, M. S., Lindley, P. F., Savage, H. F. J., Fligh-resolution neutron study of vitamin-B12 coenzyme at 15-k - structure-analysis and comparison with the structure at 279-K. Acta Crystallogr. Sect. B-Struct. Commun. 1993, 49, 79-89. 

Our neutron study of the thallium and silver derivatives was stimulated by two factors. First, T1 and Ag are excellent neutron... 

This rather unexpected result stimulated a number of other investigations, including the present one, with the conclusion that the 4 0 ordering scheme is correct.(13) In addition, the NMR and neutron diffraction data reported in referenced) have been re-interpreted in favor of 4 0 rather than 3 1 order,(14, 15) and it is concluded that the rhombohedral distrotion observed in the neutron pattern is strongly dependent upon the identity of the exchangeable cations. However, in an independent neutron study of Na-A zeolite(16), Adams and Haselden reported no evidence for such a distortion, and conclude that the symmetry must depend subtly upon the method of preparation. 

The structure of nitroimidazoles has been studied more thoroughly and can be explained by wide application of these compounds, especially in medicine. In Table 3.3 some structural characteristics (X-ray and neutron study) for the imidazole and 2-nitroimidazole derivatives are given. 

Hydrogen-bonding geometry Is virtually Identical from X-ray and neutron studies except for H - O distances. In a comparison of crystallographic data ob-... 

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