scholarly journals Lanthanum Influence onEuAlO3Perovskite Structural Properties: Experimental and Molecular Dynamics Studies

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Enrique Lima ◽  
María Elena Villafuerte-Castrejón ◽  
José Saniger ◽  
Victor Lara ◽  
Jorge E. Sánchez-Sánchez ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Structural Properties ◽  
Mas Nmr ◽  
Ftir Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lanthanum Ions ◽  
Simulation Results ◽  
Dynamics Simulations

X-ray diffraction,27Al MAS NMR, and FTIR spectra along with results of molecular dynamics simulations were used to characterise LaxEu1−xAlO3perovskites forx=0.3,  0.1. Experimental and simulation results show that local changes in the perovskite-like structure can be achieved as lanthanum ions substitute europium ones. The introduction of La3+ions in the EuAlO3parent causes an increase in the mobility of oxygen network.

scholarly journals Crystal structure of Ag-exchanged levyne intergrown with erionite: Single-crystal X-ray diffraction and Molecular Dynamics simulations

2020 ◽  
Vol 105 (11) ◽  
pp. 1631-1638 ◽  
Author(s):  
Georgia Cametti ◽  
Sergey V. Churakov
Keyword(s):  
Molecular Dynamics ◽  
Single Crystal ◽  
Molecular Dynamics Simulations ◽  
Exchange Process ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
Threefold Axis ◽  
Space Group ◽  
X Ray ◽  
Dynamics Simulations

Abstract The modification of natural zeolites via ion exchange is an efficient technique used to improve their performances and tune their properties for specific applications. In this study, a natural levyne-Ca intergrown with erionite was fully exchanged by Ag+ and its structure [with idealized chemical composition Ag6(Si,Al)18O36·18H2O] was investigated by combining a theoretical and experimental approach. Single-crystal X-ray diffraction data demonstrated that Ag-levyne maintained the R3m space group, characteristic of the natural levyne. Ag ions distribute over partially occupied sites along the threefold axis and, differently from the pristine material, at the wall of the 8-membered ring window of the lev cavity. The lack of ~30% of Ag ions that could not be located by the structural refinement is ascribed to the strong disorder of the extraframework occupants. The structural results obtained by Molecular Dynamics simulations are in overall agreement with the experimental data and showed that, on average, Ag+ is surrounded by ~2 H2O and 1 framework oxygen at distances between 2.43 and 2.6 Å. Molecular Dynamics trajectories indicate that the occurrence of silver inside the D6R cage depends on the water content: silver occupancy of D6R cages is estimated to be 83, 30, and 0% when the structure contains 3, 2.5, and 2 H2O per Ag ion, respectively. The cation-exchange process, as demonstrated by scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS) spectrometry, affects the intergrown erionite as well. A structural characterization of the Ag-erionite phase (with dimension <100 μm) was possible by means of a CuKα micro-focus source: structure solution pointed to P63/mmc space group, indicating no change with respect to natural erionite. In agreement with previous studies, K ions in the cancrinite cage could not be exchanged, whereas Ag+ is found in the eri cavity.

scholarly journals Structure and Stability of Microvoids in a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
R. Biswas ◽  
I. Kwon
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Structural Properties ◽  
Small Angle ◽  
Limited Range ◽  
Dangling Bonds ◽  
X Ray ◽  
X Ray Scattering ◽  
Internal Surfaces ◽  
Dynamics Simulations

Microvoids have been observed in a-Si:H as demonstrated by small angle X-ray scattering. We have studied the structural properties of these microvoids with molecular dynamics simulations. Using molecular dynamics simulations with classical potentials, we have created microvoids by removing Si and H atoms from a computer generated a-Si:H network. The internal surfaces of the microvoids were passivated with additional H atoms and the microvoids were fully relaxed. Microvoids over a limited range of sizes (5-90 missing atoms) were examined. We obtained a relaxed microvoid structure with no dangling bonds for a microvoid with 17 missing atoms, whereas other sizes examined produced less relaxed models with short H-H distances at the microvoid surface. The strains near the microvoid surface are described. The microvoid model was stable to local excitations on weak bonds in the vicinity of the microvoid.

scholarly journals [UO2(NH3)5]Br2·NH3: synthesis, crystal structure, and speciation in liquid ammonia solution by first-principles molecular dynamics simulations

2015 ◽  
Vol 44 (16) ◽  
pp. 7332-7337 ◽  
Author(s):  
Patrick Woidy ◽  
Michael Bühl ◽  
Florian Kraus
Keyword(s):  
Crystal Structure ◽  
Molecular Dynamics ◽  
Bond Strength ◽  
Molecular Dynamics Simulations ◽  
First Principles ◽  
Liquid Ammonia ◽  
Ammonia Solution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dynamics Simulations

X-Ray diffraction and Car–Parrinello molecular dynamics simulations furnish insights into the speciation of uranyl(vi) in liquid ammonia, calling special attention to the effect of solvation on the U–N bond length and bond strength.

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