Computer Simulation of Laser-Induced Ultrarapid Phase Changes

1988 ◽  
Vol 100 ◽  
Author(s):  
Myron T. Maclin ◽  
Michael J. Sabochick ◽  
James P. Mills
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulation ◽  
Phase Change ◽  
Phase Changes ◽  
Analytical Models ◽  
Change Models ◽  
Lennard Jones ◽  
Analytical Phase ◽  
Molecular Dynamics Results

ABSTRACTThe results of a molecular dynamics study of phase change in a system of condensed Lennard-Jones atoms is presented. These molecular dynamics results are compared to the rates of phase change predicted by two analytical phase change models. Both analytical models are supported by the molecular dynamics results.

scholarly journals A variational approach to nucleation simulation

2016 ◽  
Vol 195 ◽  
pp. 557-568 ◽  
Author(s):  
Pablo M. Piaggi ◽  
Omar Valsson ◽  
Michele Parrinello
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulation ◽  
Free Energy ◽  
Variational Approach ◽  
Sampling Method ◽  
Enhanced Sampling ◽  
Technical Problems ◽  
Lennard Jones ◽  
Dynamics Simulations

We study by computer simulation the nucleation of a supersaturated Lennard-Jones vapor into the liquid phase. The large free energy barriers to transition make the time scale of this process impossible to study by ordinary molecular dynamics simulations. Therefore we use a recently developed enhanced sampling method [Valsson and Parrinello, Phys. Rev. Lett.113, 090601 (2014)] based on the variational determination of a bias potential. We differ from previous applications of this method in that the bias is constructed on the basis of the physical model provided by the classical theory of nucleation. We examine the technical problems associated with this approach. Our results are very satisfactory and will pave the way for calculating the nucleation rates in many systems.

Computer simulation study of fluorocarbon phosphate surfactant based aqueous reverse micelle in supercritical CO2: roles of surfactant functional groups, ionic strength, and phase changes in CO2

2020 ◽  
Vol 22 (6) ◽  
pp. 3434-3445 ◽  
Author(s):  
Youngseon Shim
Keyword(s):  
Carbon Dioxide ◽  
Molecular Dynamics ◽  
Computer Simulation ◽  
Ionic Strength ◽  
Computer Simulations ◽  
Simulation Study ◽  
Supercritical Co2 ◽  
Dynamic Properties ◽  
Phase Changes ◽  
Computer Simulation Study

Structural and dynamic properties of an aqueous micelle organized from fluorocarbon phosphate surfactant molecules in supercritical carbon dioxide are investigated via molecular dynamics computer simulations.

Molecular Dynamics Computer Simulation of the Rupture of the two - Dimensional Lennard - Jones Film

1990 ◽  
Vol 188 ◽  
Author(s):  
John F. Maguire ◽  
Chun- Pok Leung
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulation ◽  
Tensile Failure ◽  
Dynamical Response ◽  
Two Dimensional ◽  
Lennard Jones ◽  
Random Forces ◽  
Internal Stress Field ◽  
Defect Nucleation ◽  
Reduced Temperature

ABSTRACTWe have conducted a molecular dynamics computer simulation of the rupture of a small, two-dimensional film. The film was composed of two hundred atoms arranged on a close-packed triangular lattice and was thermally equilibrated at a reduced temperature of 0.05. Following equilibration, the rupture characteristics of the film were investigated under tensile loading, and the atomistic dynamical response was followed throughout the rupture process. An estimate of the internal stress field was made by performing a time average over the random forces. In tensile failure, the system undergoes an initial elastic deformation followed by plastic flow. The fundamental mechanisms of defect nucleation are briefly discussed.

Formation of Polyelectrolyte Brushes on Plate

2013 ◽  
Vol 749 ◽  
pp. 588-590
Author(s):  
Yang Yang ◽  
Chun Cheng Zuo ◽  
Yu Xin Zuo ◽  
Ying Yu
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulation ◽  
Positive Charge ◽  
Coarse Grained ◽  
Lennard Jones Potential ◽  
Molecular Models ◽  
Jones Potential ◽  
Polyelectrolyte Brushes ◽  
Lennard Jones ◽  
Adsorption Density

The adsorption of polyelectrolyte chains on plate are studied using coarse-grained, bead-spring molecular models and Molecular dynamics computer simulation. It has been applied for studying the formation of polyelectrolyte brushes confined in the plates via the Lennard-Jones potential. The simulation result shows that the polyelectrolyte chains adsorption density is strongly affected by the length of the block carries the positive charge. Correspondingly, the counterions are added to the system. Upon changing the polyelectrolyte chain length N from 8 to 48, the profile of adsorption density decline between N=8 to N=18, and then rise. It has a minimum at N=18.These initial findings can be used as a guide for the preparation of actual polyelectrolyte brushes on plate by the adsorption approach.

scholarly journals Molecular Dynamics of the Phase Transition in Compressible Ammonium Chloride

1984 ◽  
Vol 37 (6) ◽  
pp. 667
Author(s):  
Sadhana Pandey ◽  
SK Trikha
Keyword(s):  
Phase Transition ◽  
Molecular Dynamics ◽  
Computer Simulation ◽  
High Pressure ◽  
Raman Spectrum ◽  
Ammonium Chloride ◽  
Dynamical Behaviour ◽  
Lennard Jones ◽  
Nearest Neighbours ◽  
Computer Simulation Technique

The effects of pressure on the dynamical behaviour of an NH: ion near the A transition under the influence of its nearest neighbours in ammonium chloride have been studied by using the computer simulation technique. The Lennard Jones (6-12) potential is used as the representative interaction between NH: and Cl-. The present calculations reveal a decrease in entropy of the system with increasing pressure. The libration frequency of the NH: ion is estimated to be approximately 170, 182 and 210 cm -1 at pressures of 1 atm, 3 and 10 kbar respectively, in agreement with the Raman spectrum study of NH4CI at high pressure (Ebisuzaki and Nicol 1969).

Influence of Metal Substitution on the Pressure-Induced Phase Change in Flexible Zeolitic Imidazolate Frameworks

2018 ◽  
Author(s):  
C. Michael McGuirk ◽  
Tomče Runčevski ◽  
Julia Oktawiec ◽  
Ari Turkiewicz ◽  
mercedes K. taylor ◽  
...  
Keyword(s):  
Phase Change ◽  
Single Crystal ◽  
Gas Adsorption ◽  
High Capacity ◽  
Phase Changes ◽  
Zeolitic Imidazolate Frameworks ◽  
Metal Substitution ◽  
Heat Management ◽  
Metal Organic ◽  
First Time

<p>Metal–organic frameworks that display step-shaped adsorption profiles arising from discrete pressure-induced phase changes are promising materials for applications in both high-capacity gas storage and energy-efficient gas separations. The thorough investigation of such materials through chemical diversification, gas adsorption measurements, and <i>in situ </i>structural characterization is therefore crucial for broadening their utility. We examine a series of isoreticular, flexible zeolitic imidazolate frameworks (ZIFs) of the type M(bim)<sub>2</sub> (SOD; M = Zn<sup> </sup>(ZIF-7), Co (ZIF-9), Cd (CdIF-13); bim<sup>–</sup> = benzimidazolate), and elucidate the effects of metal substitution on the pressure-responsive phase changes and the resulting CO<sub>2</sub> and CH<sub>4</sub> step positions, pre-step uptakes, and step capacities. Using ZIF-7 as a benchmark, we reexamine the poorly understood structural transition responsible for its adsorption steps and, through high-pressure adsorption measurements, verify that it displays a step in its CH<sub>4 </sub>adsorption isotherms. The ZIF-9 material is shown to undergo an analogous phase change, yielding adsorption steps for CO<sub>2</sub> and CH<sub>4</sub> with similar profiles and capacities to ZIF-7, but with shifted threshold pressures. Further, the Cd<sup>2+</sup> analogue CdIF-13 is reported here for the first time, and shown to display adsorption behavior distinct from both ZIF-7 and ZIF-9, with negligible pre-step adsorption, a ~50% increase in CO<sub>2</sub> and CH<sub>4</sub> capacity, and dramatically higher threshold adsorption pressures. Remarkably, a single-crystal-to-single-crystal phase change to a pore-gated phase is also achieved with CdIF-13, providing insight into the phase change that yields step-shaped adsorption in these flexible ZIFs. Finally, we show that the endothermic phase change of these frameworks provides intrinsic heat management during gas adsorption. </p>

Multicanonical Molecular Dynamics Simulation Study of the Liquid-Solid and Solid-Solid Transitions in Lennard-Jones Clusters

2011 ◽  
Author(s):  
Toshihiro Kaneko ◽  
Kenji Yasuoka ◽  
Ayori Mitsutake ◽  
Xiao Cheng Zeng
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Transition Temperature ◽  
Peak Position ◽  
Temperature Curve ◽  
Dynamics Simulation ◽  
Lennard Jones ◽  
Dynamics Simulations ◽  
First Time ◽  
Good Agreement

Multicanonical molecular dynamics simulations are applied, for the first time, to study the liquid-solid and solid-solid transitions in Lennard-Jones (LJ) clusters. The transition temperatures are estimated based on the peak position in the heat capacity versus temperature curve. For LJ31, LJ58 and LJ98, our results on the solid-solid transition temperature are in good agreement with previous ones. For LJ309, the predicted liquid-solid transition temperature is also in agreement with previous result.

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