Data Structure Determination Research Articles

New synthesis of pure orthorhombic Mo-V-A oxide phases, where A = Sb, Bi and Pb, and testing for the oxidation of light alkanes

A new, microwave-assisted technique has been developed for the synthesis of microporous vanado-molybdate catalysts with an M1-type orthorhombic structure. This method allows various cations such as Sb, Bi and - for the first time - Pb, to be introduced into the hexagonal channels of the structure, without using any expensive structure directing agent. The influence of the aforementioned elements with lone pairs of electrons on the framework structure has been studied, and the crystalline structure of the Pb-containing phase was refined using the Rietveld method and powder diffraction data. The structure determination data are in good agreement with those obtained by different analytical or spectroscopic techniques. The catalytic properties of the catalysts have been determined for the oxidative dehydrogenation of ethane, and for the oxidation of propane into acrylic acid.

Gas chromatography/mass spectrometry of trimethylsilyl derivatives of nicotianamine and related amino acids

Some trimethylsilyl derivatives of nicotianamine and related amino acids have been studied by capillary gas chromatography/mass spectrometry. This method gives useful data for structure determination.

Structure refinement from systematic row integrated intensities and non-systematic critical voltages

Renewed interest in the quantitative side of electron diffraction may be due to several factors: •convergent beam diffraction is reckognized as a source for precise and useful intensity data for structure determination;•structural features where electron diffraction offers high sensitivity, e.g. disorder, defects, transformation structures and microstructures, charge distributions, receive increasing attention in solid state research. Various approaches and applications of electron diffraction to structure determination and refinement have been reported in recent years,. In our lab we have concentrated on two methods: the non-systematical critical voltage effect applied to a inner reflections from small unit cells; intensity profiles and integrated intensities from reflections in a systematic row. Applications include charge distributions and ionicities, refinement of coordinates and thermal parameters, supplement to X-ray structure determinations.The studies of charge distribution combine two basic features of electron difraction: the high sensitivity of inner reflections to charge transfer, cf the Mott formula