A Novel Integrated X‐ray Powder Diffraction (XRPD) and Molecular Dynamics (MD) Approach for Modelling Mixed‐Metal (Zn, Al) Layered Double Hydroxides (LDHs)

Abstract

A combination of experimental (XRPD) and computational (MD-simulation) techniques was used for a detailed study of the structural, dynamic and hydration properties of the ZnAl layered double hydroxides (LDHs) of formula [Zn 0.65 , with y = 0.35 and 0.69, respectively. Our approach was based on a direct comparison made, for the first time, between the observed XRPD diffraction pattern and the MD-simulated pattern of each model that was considered. The XRPD curve is affected (reflection angles and line shapes) by dynamic and structural factors, and the interlayer distribution of the water content. Accordingly, its reproduction through MD modelling is the most suitable means of monitoring these properties of the material. Molecular modelling was performed by MD simulations of models of I and II built up through appropriate modifications of their interlayer total water contents and related distribution. The validated models, namely those that provided the best MD-simulated pattern of I and II, were then used to determine structures

DFT simulation of Mg/Al hydrotalcite with different intercalated anions: Periodic structure and solvating effects on the iodide/triiodide redox couple

“…The inorganic layer structure is rigid and very small variations are observed with the different anions: the optimized metal-metal distance is always 3.08 Å, and the metaloxygen distance is 2.07-2.08 Å, to be compared with the experimental values of 3.07 and 2.01 Å, respectively [18,21].…”

“…Though XRPD pattern analysis indicate that 2:1 hydrotalcite belongs to rhombohedral R 3m space group [18,21], we adopted the non-symmetric P1 group for all the calculations, to allow the intercalated groups to move freely during the geometry optimizations, even if at the price of larger unit cells. The crystal structures were optimized with successive steps, alternating the optimization of atomic positions inside the unit cell and of the 3D periodic parameters, until self-consistency was reached.…”

“…The importance of HT in so many fields of chemistry and chemical engineering has motivated several recent structural studies of hydrotalcite with different composition and different intercalated anions [12,13,[18][19][20][21][22][23][24][25][26]. Also organic anions, in some cases quite large, have been successfully intercalated, confirming the high flexibility of HT layered structure [27].…”

From the X-rays to a reliable “low cost” computational structure of caffeic acid: DFT, MP2, HF and integrated molecular dynamics–X-ray diffraction approach to condensed phases

“…The picture was even more confused after considering the results from HF method, which seem to be in agreement with the DFT calculations. For condensed phase simulations the MD scheme, especially when combined with X-ray diffraction data, gives the possibility to attain structural information that are otherwise inaccessible [29][30][31][32][33]. Moreover, this technique provides the ability to immediately monitor the internal molecular fluctuations, which are directly comparable with those obtained by diffraction data [34], giving in this way a tool for validating the simulated trajectory.…”

Molecular dynamics simulation of anionic clays containing glutamic acid

“…The average a-unit cell dimensions computed from NPT-ensemble MD simulations are 2.715 Å, slightly less than the crystallographic data of 3.075 Å [32]. The snapshots of Glu-LDH with different increasing water contents (N w = 4, 12, 28, 36, 44, 52) were 4) Interlayer water molecules not only filled in the space between the anions, a well-ordered structural water layer was also formed on the surface hydroxyls of Glu-LDH.…”