Study of Aqueous Acetone Solution at Various Concentrations:  Low-Frequency Raman and Molecular Dynamics Simulations

2001 ◽  
Vol 105 (25) ◽  
pp. 6004-6009 ◽  
Author(s):  
A. Idrissi ◽  
S. Longelin ◽  
F. Sokolić
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Low Frequency ◽  
Aqueous Acetone ◽  
Acetone Solution ◽  
Dynamics Simulations ◽  
Aqueous Acetone Solution

Molecular Dynamics Simulations of Low-Energy Atom-Surface Interactions

1992 ◽  
Vol 268 ◽  
Author(s):  
J. A. Sprague ◽  
C. M. Gilmore
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Film Growth ◽  
Low Frequency ◽  
Exchange Interactions ◽  
Low Energy ◽  
Growth Surface ◽  
Surface Exchange ◽  
Oriented Film ◽  
Dynamics Simulations

ABSTRACTMolecular dynamics simulations of the deposition of atoms on crystalline surfaces have been conducted using the embedded atom method. The following atom-substrate combinations have been employed: 0.1 - 40 eV Ag deposited on (111) and (100) Ag substrates; 0.1 eV Ag deposited on (100) Cu; and 0.1 eV Cu deposited on (100) Ag. The purpose of the calculations for Ag atoms deposited on Ag substrates was to investigate the effects of adatom arrival energy and substrate orientation on the interactions of low-energy atoms with crystal surfaces. The goal of tile Ag oil Cu and Cu on Ag calculations was to observe the mechanisms producing thepreviously-reported asymmetry in epitaxy for these systems. The Ag on Ag deposition simulations demonstrated that the effects of increased atom arrival energies in promoting layerby- layer film growth and producing diffuse substrate-filn interfaces (mixing) were basically the same on the (100) and (111) surfaces. At 0. 1 eV, representative of thennal evaporation, the degree of island formation on the (100) substrate was essentially tile same as previously reported for a (111) Ag substrate. At a given atom arrival energy between 10 and 40 eV, both the redistribution into full monolayers and the mixing by surface exchange interactions were seen to occur more readily on the close-packed (111) growth surface than on the more open (100) surface. The mixing was a stronger function of crystallographic orientation. Cu was observed to grow on (100) Ag as a (100)-oriented film, with the initial film layers transfonned essentially to the bcc structure by a Bain distortion, in agreement with various experimental results. The distortion of the film layers resulted in large-amplitude soft-mode (low-frequency) lattice vibrations. Ag was observed to grow on (100) Cu as a (111)-oriented film, as experimentally observed, with the <110>-type orientations of film and substrate parallel, as predicted by previous calculations of interfacial energy.

Molecular Dynamics Simulations of Porous Silica

1997 ◽  
Vol 492 ◽  
Author(s):  
J.V.L. Beckers ◽  
S. W. De Leeuw
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Porous Silica ◽  
Power Spectra ◽  
Low Frequency ◽  
Internal Surface ◽  
Simulation Method ◽  
Porous Network ◽  
Long Range Correlations ◽  
Dynamics Simulations

ABSTRACTWe describe a new simulation method for the preparation of porous silica and present results from molecular dynamics simulations of the structures obtained. We start from a homogeneous liquid phase with reduced atomic charges. The charges are then slowly rescaled and the atoms start clustering to finally form a porous network. We observe that local ordering precedes formation of long range correlations. We investigate physical properties of porous silica such as porosity, internal surface and fractality. They are in reasonable agreement with experimental data, although internal surface and porosity seem to be systematically larger than those found in adsorption experiments. The vibrational and dielectric power spectra show an enhanced intensity in the low frequency region. These modes can be associated with slow dynamics of clusters.

Inelastic neutron scattering and molecular dynamics studies on low-frequency modes of clathrate hydrates

2003 ◽  
Vol 81 (1-2) ◽  
pp. 493-501 ◽  
Author(s):  
H Itoh ◽  
B Chazallon ◽  
H Schober ◽  
K Kawamura ◽  
W F Kuhs
Keyword(s):  
Molecular Dynamics ◽  
Neutron Scattering ◽  
Molecular Dynamics Simulations ◽  
Inelastic Neutron Scattering ◽  
Low Frequency ◽  
Inelastic Neutron ◽  
Host Lattice ◽  
Clathrate Hydrates ◽  
Type I ◽  
Dynamics Simulations

Low-frequency modes of gas hydrates with Xe, Ar, O2, and N2 atoms/molecules have been studied by inelastic neutron-scattering and molecular dynamics simulations. Type I and type II clathrate hydrates show some small but significant differences of the low-frequency host contribution to the density of states. Both differ markedly from that of ice Ih and depend only weakly on the guest. The vibrational modes associated with Xe atoms were observed at 2.2, 2.9, and 4.0 meV (T = 100 K). They are in good agreement with predictions from molecular dynamics simulations. In the case of N2 hydrate we found a well-defined peak at about 2 meV, which shows a remarkable shift to higher frequency with increasing temperature. This peak and a broad peak that is overlapped with the host lattice modes (6.5 and 10.5 meV) are assigned to the vibration of N2 molecules in the large and small cages, respectively. The calculated vibrational spectra of N2 molecules in doubly occupied large cages show a significant distinct spectral distribution. The anharmonic shift of the guest atoms in large cages is significantly less pronounced in Xe hydrates suggesting that guest-host interactions can vary considerably from one system to another. PACS Nos.: 82.75-z, 78.70N, 71.15Pd, 63

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