Topological Analysis of the Interactions between Organic Molecules and Co(Ni)MoS Catalytic Active Phases

What is a local viewpoint of delocalized bonds? We try to provide an answer to this paradoxical question by investigating representative conjugated organic molecules (namely, allyl cation, trans-butadiene, and benzene) together with reference nonconjugated systems (ethylene and propene) by means of topological analysis of the electron localization function ELF. The valence attractors of the ELF gradient field are classified according to their synaptic order (i.e., connections with core attractors). The basin populations [Formula: see text] (i.e., the integrated density over the attractor basins) and their standard deviation, σ, have been calculated and are discussed. The basin populations and their relative fluctuations, defined as [Formula: see text] are sensitive criteria of delocalization. In the case of well-localized C—C or C=C bonds, λ ~0.4, whereas for delocalized bonds λ increases to about 0.5. Another criterion of delocalization is provided by the basin hierarchy, which is defined from the reduction of the localization domains. For most systems, delocalization occurs not only for neighboring carbon-carbon disynaptic attractor basins, but also for nearest neighbor disynaptic protonated attractor basins. Key words: electron localization function, topological analysis, delocalization, population analysis.

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High Resolution Replication of Organoclay Surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055126 ◽

1982 ◽

Vol 40 ◽

pp. 576-577

Author(s):

W. W. Barker ◽

W. E. Rigsby ◽

V. J. Hurst ◽

W. J. Humphreys

Keyword(s):

Clay Mineral ◽

Organic Molecule ◽

Organic Molecules ◽

X Ray Diffraction ◽

Xrd Pattern ◽

X Ray ◽

Naturally Occurring ◽

Silicate Layers ◽

Mineral Identification

Experimental clay mineral-organic molecule complexes long have been known and some of them have been extensively studied by X-ray diffraction methods. The organic molecules are adsorbed onto the surfaces of the clay minerals, or intercalated between the silicate layers. Natural organo-clays also are widely recognized but generally have not been well characterized. Widely used techniques for clay mineral identification involve treatment of the sample with H2 O2 or other oxidant to destroy any associated organics. This generally simplifies and intensifies the XRD pattern of the clay residue, but helps little with the characterization of the original organoclay. Adequate techniques for the direct observation of synthetic and naturally occurring organoclays are yet to be developed.

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Direct phase determination in electron crystallography: small organic molecules

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130468 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1166-1167

Author(s):

Douglas L. Dorset

Keyword(s):

Organic Molecules ◽

Data Sets ◽

Temperature Structure ◽

3D Analysis ◽

Intensity Data ◽

Electron Crystallography ◽

Phase Determination ◽

Measured Intensity ◽

3D Data

The quantitative use of electron diffraction intensity data for the determination of crystal structures represents the pioneering achievement in the electron crystallography of organic molecules, an effort largely begun by B. K. Vainshtein and his co-workers. However, despite numerous representative structure analyses yielding results consistent with X-ray determination, this entire effort was viewed with considerable mistrust by many crystallographers. This was no doubt due to the rather high crystallographic R-factors reported for some structures and, more importantly, the failure to convince many skeptics that the measured intensity data were adequate for ab initio structure determinations.We have recently demonstrated the utility of these data sets for structure analyses by direct phase determination based on the probabilistic estimate of three- and four-phase structure invariant sums. Examples include the structure of diketopiperazine using Vainshtein's 3D data, a similar 3D analysis of the room temperature structure of thiourea, and a zonal determination of the urea structure, the latter also based on data collected by the Moscow group.

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