Crystal structure and enantiomeric layer disorder of a copper(I) nitrate π-coordination compound

The novel π-coordination compound [CuI(m-dmphast)NO3], where m-dmphast = 5-(allylthio)-1-(3,5-dimethylphenyl)-1H-tetrazole, is characterized using single-crystal X-ray diffraction and crystallizes in a noncentrosymmetric space group. Additionally, for the first time in this group of materials, the streaks of X-ray diffuse scattering in the reciprocal space sections were observed and described. This gave the possibility for a deeper insight into the local structure of the title compound. The conjecture about the origin of diffuse scattering was derived from average structure solution. It was then confirmed using the local structure modelling. The extended [Cu(m-dmphast)NO3]∞ chains, connected by weak interactions, produce layers which can exist in two enantiomeric forms, one of which predominates.

Differential evolution and Markov chain Monte Carlo analyses of layer disorder in nanosheet ensembles using total scattering

Assemblies of nanosheets are often characterized by extensive layer-position disorder. Coupled with the often minute coherent scattering domain size and relaxation of the nanosheet structure itself, unambiguous interpretation of X-ray and neutron scattering data from such materials is non-trivial. This work demonstrates a general approach towards refinement of layer-disorder information from atomic pair distribution function (PDF) data for materials that span the gap between turbostratism and ordered stacking arrangements. X-ray total scattering data typical of a modern rapid-acquisition PDF instrument are simulated for a hypothetical graphene-like structure using the program DIFFaX, from which atomic PDFs are extracted. Small 1 × 1 × 20 supercell models representing the stacking of discrete layer types are combined to model a continuous distribution of layer-position disorder. Models optimized using the differential evolution algorithm demonstrate improved fit quality over 75 Å when a single mean layer-type model is replaced with a constrained 31-layer-type model. Posterior distribution analyses using the Markov chain Monte Carlo algorithm demonstrate that the influence of layer disorder and finite particle size are correlated. However, the refined mean stacking vectors match well with the generative parameter set.

Investigations on Microstructural and Layer Disorder Parameters of Na-Montmorillonite-Glycine Intercalation Compounds

Glycine-Montmorillonite (Gly-MMT) composite has been synthesized through intercalation process using Na-Montmorillonite (Na- MMT) and glycine ethylester hydrochloride. Gly-MMT was employed for the synthesis of dipeptide (Gly-Gly-MMT). Microstructural parameters such as crystallite size, r.m.s. strain (<e2>1/2) and layer disorder parameters such as variation of interlayer spacing (g) and proportion of planes affected by such defects (?) of the samples have been calculated by X-ray line profile analysis. In comparison to Na-MMT the basal spacings (d001) of Gly-MMT and Gly-Gly-MMT were reduced by 2.4Å and 1.8Å respectively. The value of d001 of Gly-Gly-MMT (13.3 Å) suggests the monolayer orientation of dipeptide into interlayer spaces. It is also suggested that more homogeneity in the stacking of silicate layers is attained in Gly-Gly-MMT due to the increased chain length of the dipeptide and orientation in monolayer style.DOI: http://dx.doi.org/10.3329/dujs.v60i1.10331Dhaka Univ. J. Sci. 60(1): 25-29, 2012 (January)

Microstructural parameters and layer disorder accompanying dehydration transformation in Na-montmorillonite

Structural changes accompanying thermal transformation in Na-montmorillonite samples up to a temperature of 500°C have been investigated by X-ray line profile analysis. The method of Fourier initial slope and variance analysis of X-ray line profiles have been used to calculate the different microstructural parameters like crystallite size, r.m.s. strain (<e