A neutron diffraction

Pings [106], and a neutron diffraction study by Mildner and Carpenter [107], both concluded that there is no clear evidence for sp carbon and that the radial distribution functions can be satisfactorily indexed to a hexagonal arrays of carbon atoms. A similar conclusion was reached in a recent neutron diffraction study of activated carbons by Gardner et al [108]. 

Except for Ceo, lack of sufficient quantities of pure material has prevented more detailed structural characterization of the fullerenes by X-ray diffraction analysis, and even for Ceo problems of orientational disorder of the quasi-spherical molecules in the lattice have exacerbated the situation. At room temperature Cgo crystallizes in a face-centred cubic lattice (Fm3) but below 249 K the molecules become orientationally ordered and a simple cubic lattice (Po3) results. A neutron diffraction analysis of the ordered phase at 5K led to the structure shown in Fig. 8.7a this reveals that the ordering results from the fact that... 

O-H bond length was 1.08A, a value similar to that previously reported by Szy-tula et al. in a neutron diffraction study of Ni(OH)2 [23]. The O-H bond is both well crystallized and as precipitated materials is parallel to the c-axis. The difference between well-crystallized and as precipitated material is important since the well-crystallized material is not electrochemi-cally active. The differences between the materials are attributed to a defective structure that accrues from the large concentration of surface OH ion groups in the high-surface-area material [22]. These are associated with absorbed water. This is a consistent with an absorption band in the infrared at 1630cm 1. This is not seen in the well-crystallized material. 

Takusagawa F, Koetzle TF (1979) A neutron diffraction study of the crystal structure of ferrocene. Acta Crystallogr B 35 1074-1081... 

P21212i Z = 4 D = 1.663 R = 0.024 for 1,863 neutron intensities at 123 K. This is a neutron-diffraction, low-temperature refinement of a partially deuterated molecule. The undeuterated molecule had previously been studied by neutron diffraction at room temperature.10 The experiment was performed in order to seek evidence of favored replacement of hydrogen by deuterium at the anomeric hydroxyl group, but no evidence therefor was observed. 

The long-known K2Hg(CN)4 and related compounds are still the object of structural studies. Thus, a neutron-diffraction study confirmed the spinel structure of K2Hg(CN)4 at room temperature (298 K) with exactly tetrahedral anions, Hg(CN)42 (r(Hg—C) 215.2, r(C—N) 114.9 pm).112... 

PI Z = 1 Dn = 1.475 R = 0.05 for 961 neutron intensities. This is a neutron-diffraction refinement of a structure previously determined by X-ray diffraction.56 All of the hydroxyl groups are involved in inter-molecular hydrogen-bonds which form infinite chains, with H O distances ranging from 175.5 to 200.2 pm, and O-H O angles... 

The dihydrogen molecule assumes a side-on terminal coordination. The W-H2 distance is 1.95 A (X-ray diffraction) or 1.89 A (neutron diffraction). The H-H distance is 0.75 A (X-ray diffraction) or 0.82 A (neutron diffraction), with respect to 0.74 A for molecular hydrogen in the gaseous state. 

The purity of the terminal Au-oxo complexes, 3 and 4, was established by several methods including P NMR (3 and 4 have only one phosphorus peak at —8.55 and —13.15 ppm, respectively), cyclic voltammetry, electronic absorption spectroscopy, vibrational spectroscopy, detailed magnetic measurements and elemental analysis on all elements (triplicate analyses for Au) (44). The single peak in the PNMR spectra is consistent with the C2V symmetry of 3 and 4 established by multiple X-ray crystallographic structure determinations and a neutron diffraction study on 3 at liquid He... 

A neutron-diffraction analysis of a single crystal of KHFj found the proton to be centred to within 100 pm (Peterson and Levy, 1952). An early nmr investigation of the H and spectra came to the same conclusion and narrowed the uncertainty to 60 pm (Waugh et al., 1953), and a later nmr analysis reduced it to 25 pm (Paratt and Smith, 1975). A neutron diffraction study of NaDFj showed this to have a centred deuterium atom with Rp. F = 226.5 pm (McGaw and Ibers, 1963). 

The structure derived from a Rietveld fit of a neutron diffraction pattern of a 6-line ferrihydrite which showed more and sharper lines (Fig. 2.9, lower) than an XRD pattern, was in agreement with the structure proposed by Drits et al. (1993) except that it was not necessary to assume the presence of hematite in order to produce a satisfactory fit (Jansen et al. 2002). The unit cell of the defect free phase had a = 0.29514(9) nm and c = 0.9414(9) nm and the average domain size derived from line broadening was 2.7(0.8) nm. Since forced hydrolysis of an Fe solution at elevated temperatures will ultimately lead to hematite, it is likely that incipient hematite formation may occur under certain synthesis conditions. Neither these studies nor Mbssbauer spectroscopy, which showed only a singular isomer shift at 4.2 K characteristic of Fe, supported the presence of " Fe (Cardile, 1988 Pankhurst Pollard, 1992). However, the presence, at the surface, of some Fe with lower (<6) coordination, perhaps as tetrahedra (Eggleton and Fitzpatrick, 1988) which may have become unsaturated on heating, has been suggested on the basis of XAFS results (Zhao et al. 1994). 

Erickson, R. A. Neutron diffraction studies of antiferromagnetism in manganous fluoride and some isomorphons compounds. Phys. Rev. 90, 779 (1953). 

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