Structural parameters of the immediate environment of ions in saturated aqueous solutions of lanthanide chlorides, according to X-ray diffraction data

2017 ◽  
Vol 91 (4) ◽  
pp. 654-657 ◽  
Author(s):  
P. R. Smirnov ◽  
O. V. Grechin
1982 ◽  
Vol 37 (10) ◽  
pp. 1205-1210 ◽  
Author(s):  
G. Licheri ◽  
G. Paschina ◽  
G. Piccaluga ◽  
G. Pinna

Five aqueous solutions of ZnSO4 of concentrations ranging from 0.6M to 3.1 M were examined by X-ray diffraction. In the correlation functions no concentration effect on structural phenomena is detectable. The same model was then successfuly used for all cases, attributing two hydration shells to Zn2+ and one hydration shell to SO42+ . The reliability of the structural parameters obtained is discussed.


Author(s):  
Pavel R. Smirnov ◽  
Oleg V. Grechin ◽  
Elena A. Voevodina

Comparatively large amount of works has been devoted to the investigation of the nearest environment of cesium ions in aqueous solutions. But up to date there are no precise quantitative parameters of it. Information about influence of concentration on cesium salts solutions structure is also absent. In order to get the coordination number of Cs+ ion and its dependence on the amount of dissolved salt the set of aqueous solutions of cesium iodide have been studied by X-ray diffraction method in wide concentration range under ambient conditions. Radial distribution functions (RDFs) of the solutions investigated have been calculated from experimental intensity curves of X-ray scattering. Interpretation of experimental peaks on RDFs has been made. On the basis of experimental results and literature information some physically reasonable models of solution have been constructed. Theoretical RDFs have been calculated for every model. Then an optimization procedure has also been made. On the ground of the best fitness between experimental and theoretical RDFs the optimal models for every solution have been found. All quantitative parameters have been tabulated and analyzed. Hydration numbers of Cs+ and I- increase with dilution, reaching in the solution of molar ratio 1:80 values 6.3 and 4.1, respectively. Interparticle distances of Cs+–ОН2 and I- –ОН2 are equal approximately to 0.312 and 0.359 nm. The ions do not form the second coordination shells. It has been determined that contact ion pairs Cs+–I- exist in whole concentration range investigated.Forcitation:Smirnov P.R., Grechin O.V., Voevodina E.A. Structure of nearest environment of ions in aqueous cesium iodide solutions from X-ray diffraction data. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 7. P. 21-26.


2015 ◽  
Vol 48 (4) ◽  
pp. 1201-1211 ◽  
Author(s):  
Anton Gagin ◽  
Igor Levin

A method has been developed to address the effects of systematic errors in Rietveld refinements using powder diffraction data. Relevant errors were categorized into multiplicative, additive and peak-shape types. Corrections for these errors were incorporated into structural refinements using a Bayesian statistics approach, with the corrections themselves treated as nuisance parameters and marginalized out of the analysis. Structural parameters refined using the proposed method represent probability-weighted averages over all possible error corrections. The developed formalism has been adapted to least-squares minimization algorithms and implemented as an extension to the Rietveld software packageGSAS-II. The technique was first tested using neutron and X-ray diffraction data simulated for PbSO4and then applied to the equivalent experimental data sets for the same compound. The results obtained using the simulated data confirmed that the proposed method yields significantly more accurate estimates of structural parameters and their uncertainties than standard refinements. The benefits were particularly significant for joint refinements using neutron and X-ray diffraction data because accounting for systematic errors enabled more adequate weighting of the individual data sets.


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