X-ray Scattering Measurements of the Ag(111) Surface Thermal Expansion

2001 ◽  
Vol 678 ◽  
Author(s):  
Cristian E. Botez ◽  
William C. Elliott ◽  
Paul F. Miceli ◽  
Peter W. Stephens
Keyword(s):  
Molecular Dynamics ◽  
Thermal Expansion ◽  
Molecular Dynamics Simulations ◽  
Temperature Interval ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Measurements ◽  
The One ◽  
Dynamics Simulations

AbstractWe have used synchrotron X-ray diffraction to study the thermal expansion of the Ag(111) surface. Throughout the temperature interval between 300 and 1100K, we observed that the separation between the first and the second atomic layers at the surface, 12 d, differs from its bulk counterpart, d, by less than 1%, indicating that the thermal expansion at the surface is similar to the one in the bulk. This result represents the first experimental confirmation of the predictions from molecular dynamics simulations, which indicate a small enhancement of the anharmonic effects at this surface.

scholarly journals Interfacial Reactivity and Speciation Emerging from Namontmorillonite Interactions with Water and Formic Acid at 200°C: Insights from Reactive Molecular Dynamics Simulations, Infrared Spectroscopy, and X-ray Scattering Measurements

2020 ◽  
Author(s):  
Murali Gopal Muraleedharan ◽  
Hassnain Asgar ◽  
Seung Ho Hahn ◽  
Nabankur Dasgupta ◽  
Greeshma Gadikota ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Formic Acid ◽  
Molecular Dynamics Simulations ◽  
Sodium Montmorillonite ◽  
X Ray ◽  
Reactive Molecular Dynamics ◽  
X Ray Scattering ◽  
Scattering Measurements ◽  
Dynamics Simulations ◽  
Ray Scattering

Reactive organic fluid - mineral interactions at elevated temperatures contribute to the evolution of planetary matter. One of the less studied but important transformations in this regard involves the reactions of formic acid with naturally occurring clays such as sodium montmorillonite. To advance a mechanistic understanding of these interactions, we use ReaxFF reactive molecular dynamics simulations in conjunction with infrared (IR) spectroscopy and X-ray scattering experiments to investigate the speciation behavior of water-formic acid mixtures on sodium montmorillonite interfaces at 473 K and 1 atm. Using a newly developed reactive forcefield, we show that the experimental IR spectra of unreacted and reacted mixture can be accurately reproduced by ReaxFF/MD. We further benchmark the simulation predictions of sodium carbonate and bicarbonate formation in the clay interlayers using Small and Wide-Angle X-ray Scattering measurements. Subsequently, leveraging the benchmarked forcefield, we interrogate the pathway of speciation reactions with emphasis on carbonate, formate, and hydroxide groups elucidating the energetics, transition states, intermediates, and preferred products. We also delineate the differences in reactivities and catalytic effects of clay edges, facets, and interlayers owing to their local chemical environments, which have far reaching consequences in their speciation behavior. The experimental and simulation approaches described in this study and the transferable forcefields can be applied translationally to advance the science of clay-fluid interactions for several applications including subsurface fluid storage and recovery and clay-pollutant dynamics

Interfacial Reactivity and Speciation Emerging from Namontmorillonite Interactions with Water and Formic Acid at 200°C: Insights from Reactive Molecular Dynamics Simulations, Infrared Spectroscopy, and X-ray Scattering Measurements

2020 ◽  
Author(s):  
Murali Gopal Muraleedharan ◽  
Hassnain Asgar ◽  
Seung Ho Hahn ◽  
Nabankur Dasgupta ◽  
Greeshma Gadikota ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Formic Acid ◽  
Molecular Dynamics Simulations ◽  
Sodium Montmorillonite ◽  
X Ray ◽  
Reactive Molecular Dynamics ◽  
X Ray Scattering ◽  
Scattering Measurements ◽  
Dynamics Simulations ◽  
Ray Scattering

Reactive organic fluid - mineral interactions at elevated temperatures contribute to the evolution of planetary matter. One of the less studied but important transformations in this regard involves the reactions of formic acid with naturally occurring clays such as sodium montmorillonite. To advance a mechanistic understanding of these interactions, we use ReaxFF reactive molecular dynamics simulations in conjunction with infrared (IR) spectroscopy and X-ray scattering experiments to investigate the speciation behavior of water-formic acid mixtures on sodium montmorillonite interfaces at 473 K and 1 atm. Using a newly developed reactive forcefield, we show that the experimental IR spectra of unreacted and reacted mixture can be accurately reproduced by ReaxFF/MD. We further benchmark the simulation predictions of sodium carbonate and bicarbonate formation in the clay interlayers using Small and Wide-Angle X-ray Scattering measurements. Subsequently, leveraging the benchmarked forcefield, we interrogate the pathway of speciation reactions with emphasis on carbonate, formate, and hydroxide groups elucidating the energetics, transition states, intermediates, and preferred products. We also delineate the differences in reactivities and catalytic effects of clay edges, facets, and interlayers owing to their local chemical environments, which have far reaching consequences in their speciation behavior. The experimental and simulation approaches described in this study and the transferable forcefields can be applied translationally to advance the science of clay-fluid interactions for several applications including subsurface fluid storage and recovery and clay-pollutant dynamics

Liquid Structure of 1-Propanol by Molecular Dynamics Simulations and X-Ray Scattering

2004 ◽  
Vol 33 (6/7) ◽  
pp. 797-809 ◽  
Author(s):  
Isao Akiyama ◽  
Masaya Ogawa ◽  
Keiichi Takase ◽  
Toshiyuki Takamuku ◽  
Toshio Yamaguchi ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Liquid Structure ◽  
X Ray ◽  
X Ray Scattering ◽  
Dynamics Simulations ◽  
Ray Scattering

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 Conformational dynamics of a crystalline protein from microsecond-scale molecular dynamics simulations and diffuse X-ray scattering

2014 ◽  
Vol 111 (50) ◽  
pp. 17887-17892 ◽  
Author(s):  
Michael E. Wall ◽  
Andrew H. Van Benschoten ◽  
Nicholas K. Sauter ◽  
Paul D. Adams ◽  
James S. Fraser ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Conformational Dynamics ◽  
X Ray ◽  
X Ray Scattering ◽  
Dynamics Simulations ◽  
Ray Scattering
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