scholarly journals Coupling between structural relaxation and diffusion in glass-forming liquids under pressure variation

2020 ◽  
Vol 22 (42) ◽  
pp. 24365-24371
Author(s):  
Anh D. Phan ◽  
Kajetan Koperwas ◽  
Marian Paluch ◽  
Katsunori Wakabayashi
Keyword(s):  
Molecular Dynamics ◽  
Langevin Equation ◽  
Structural Relaxation ◽  
Md Simulations ◽  
Pressure Variation ◽  
Glass Forming ◽  
Nonlinear Langevin Equation ◽  
And Diffusion

We theoretically investigate structural relaxation and activated diffusion of glass-forming liquids at different pressures using both Elastically Collective Nonlinear Langevin Equation (ECNLE) theory and molecular dynamics (MD) simulations.

scholarly journals Effects of cooling rate on structural relaxation in amorphous drugs: elastically collective nonlinear langevin equation theory and machine learning study

RSC Advances ◽  
2019 ◽  
Vol 9 (69) ◽  
pp. 40214-40221 ◽  
Author(s):  
Anh D. Phan ◽  
Katsunori Wakabayashi ◽  
Marian Paluch ◽  
Vu D. Lam
Keyword(s):  
Machine Learning ◽  
Cooling Rate ◽  
Langevin Equation ◽  
Structural Relaxation ◽  
Molecular Mobility ◽  
Learning Study ◽  
Cooling Rates ◽  
Theoretical Approaches ◽  
Amorphous Drugs ◽  
Nonlinear Langevin Equation

Theoretical approaches are formulated to investigate the molecular mobility under various cooling rates of amorphous drugs.

Energetics and diffusion of liquid water and hydrated ions through nanopores in graphene: ab initio molecular dynamics simulation

2017 ◽  
Vol 19 (31) ◽  
pp. 20551-20558 ◽  
Author(s):  
Raúl Guerrero-Avilés ◽  
Walter Orellana
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Ab Initio Molecular Dynamics ◽  
Functional Theory ◽  
Hydrated Ions ◽  
And Diffusion

The energetics and diffusion of water molecules and hydrated ions (Na+, Cl−) passing through nanopores in graphene are addressed by dispersion-corrected density functional theory calculations and ab initio molecular dynamics (MD) simulations.

Universal Trend of the Non-Exponential Rouse Mode Relaxation in Glass-Forming Polymers Systems: Experimental Facts, MD-Simulation Results and a Theoretical Approach Based on a Generalized Langevin Equation

MRS Advances ◽  
2016 ◽  
Vol 1 (26) ◽  
pp. 1903-1913 ◽  
Author(s):  
J. Colmenero
Keyword(s):  
Langevin Equation ◽  
Theoretical Approach ◽  
Md Simulation ◽  
Memory Function ◽  
Md Simulations ◽  
Generalized Langevin Equation ◽  
Exponential Behavior ◽  
Glass Forming ◽  
Chain Stiffness ◽  
Local Potentials

ABSTRACTNowadays there are clear evidences from both experiments and MD-simulations proving that the chain Rouse modes correlation functions are non-exponential in unentangled polymer blends and also in pure polymers at low temperature (with respect to that of the glass transition Tg) even for the long wavelengths modes where local potentials and chain stiffness should not play any role. In a recent paper [S. Arrese-Igor et al, Phys. Rev. Lett.113, 078302 (2014)] it has been proposed that this non-exponential behavior depends on the ratio between the so-called Rouse time - i.e., the characteristic time of the slowest chain mode relaxation - and the time scale of the α-relaxation. This parameter is in some way ‘universal’ in the meaning that it can encode many different experimental situations. In this paper, we show that this behavior can be quantitatively explained in the framework of a theoretical approach based on: (i) a generalized Langevin equation (GLE) formalism and (ii) a memory function which takes into account the effect of collective dynamics on the chain dynamics of a tagged chain and which was constructed taking inspirations from the original ideas of the reptation model proposed by de Gennes.

Local Atomic Arrangements of Pd-Based Bulk Metallic Glasses of the Metal-Metalloid Type Demonstrated by Molecular Dynamics Simulations

2010 ◽  
Vol 654-656 ◽  
pp. 1038-1041
Author(s):  
Akira Takeuchi ◽  
Akihisa Inoue
Keyword(s):  
Molecular Dynamics ◽  
Metallic Glasses ◽  
Md Simulations ◽  
Glass Forming Ability ◽  
Plastic Crystal ◽  
Glass Forming ◽  
Universal Feature ◽  
Crystal Model ◽  
Packed Structure ◽  
Dynamics Simulations

Molecular dynamics (MD) simulations based on a plastic crystal model (PCM) were performed for a Pd0.4Ni0.4P0.2 alloy in Metal-Metalloid (M-MLD) type of bulk metallic glass (BMG). Two kinds of clusters of cubeoctahedron capped with four half-octahedra and trigonal prism were used as initial atomic arrangements of the Pd0.4Ni0.4P0.2 alloy. Random rotations of clusters around their centers of gravity and subsequent structural relaxation vitrified the alloy. The high glass-forming ability of the Pd0.4Ni0.4P0.2 alloy is due to the critically-percolated, cluster-packed structure that is a universal feature for both M-MLD and M-M types of BMGs.

Disjoining Pressure Effects in Ultra-Thin Liquid Films in Micropassages—Comparison of Thermodynamic Theory With Predictions of Molecular Dynamics Simulations

2006 ◽  
Vol 128 (12) ◽  
pp. 1276-1284 ◽  
Author(s):  
V. P. Carey ◽  
A. P. Wemhoff
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Vapor Pressure ◽  
Film Thickness ◽  
Md Simulation ◽  
Heat Pipes ◽  
Md Simulations ◽  
Disjoining Pressure ◽  
Pressure Variation ◽  
Equilibrium Vapor Pressure

The concept of disjoining pressure, developed from thermodynamic and hydrodynamic analysis, has been widely used as a means of modeling the liquid-solid molecular force interactions in an ultra-thin liquid film on a solid surface. In particular, this approach has been extensively used in models of thin film transport in passages in micro evaporators and micro heat pipes. In this investigation, hybrid μPT molecular dynamics (MD) simulations were used to predict the pressure field and film thermophysics for an argon film on a metal surface. The results of the simulations are compared with predictions of the classic thermodynamic disjoining pressure model and the Born-Green-Yvon (BGY) equation. The thermodynamic model provides only a prediction of the relation between vapor pressure and film thickness for a specified temperature. The MD simulations provide a detailed prediction of the density and pressure variation in the liquid film, as well as a prediction of the variation of the equilibrium vapor pressure variation with temperature and film thickness. Comparisons indicate that the predicted variations of vapor pressure with thickness for the three models are in close agreement. In addition, the density profile layering predicted by the MD simulations is in qualitative agreement with BGY results, however the exact density profile is dependent upon simulation parameters. Furthermore, the disjoining pressure effect predicted by MD simulations is strongly influenced by the allowable propagation time of injected molecules through the vapor region in the simulation domain. A modified thermodynamic model is developed that suggests that presence of a wall-affected layer tends to enhance the reduction of the equilibrium vapor pressure. However, the MD simulation results imply that presence of a wall layer has little effect on the vapor pressure. Implications of the MD simulation predictions for thin film transport in micro evaporators and heat pipes are also discussed.

Disjoining Pressure Effects in Ultra-Thin Liquid Films in Micropassages: Comparison of Thermodynamic Theory With Predictions of Molecular Dynamics Simulations

2005 ◽  
Author(s):  
V. P. Carey ◽  
A. P. Wemhoff
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Vapor Pressure ◽  
Film Thickness ◽  
Md Simulation ◽  
Heat Pipes ◽  
Md Simulations ◽  
Disjoining Pressure ◽  
Pressure Variation ◽  
Equilibrium Vapor Pressure

The concept of disjoining pressure, developed from thermodynamic and hydrodynamic analysis, has been widely used as a means of modeling the liquid-solid molecular force interactions in an ultra-thin liquid film on a solid surface. In particular, this approach has been extensively used in models of thin film transport in passages in micro evaporators and micro heat pipes. In this investigation, hybrid μPT molecular dynamics (MD) simulations were used to predict the pressure field and film thermophysics for an argon film on a metal surface. The results of the simulations are compared with predictions of the classic thermodynamic disjoining pressure model. The thermodynamic model provides only a prediction of the relation between vapor pressure and film thickness for a specified temperature. The MD simulations provide a detailed prediction of the density and pressure variation in the liquid film, as well as a prediction of the variation of the equilibrium vapor pressure variation with temperature and film thickness. Comparisons indicate that the predicted variations of vapor pressure with thickness for these two models are in close agreement. A modified thermodynamic model is developed which suggests that presence of a wall-affected layer tends to enhance the reduction of the equilibrium vapor pressure. However, the MD simulation results imply that presence of a wall layer has little effect on the vapor pressure. Implications of the MD simulation predictions for thin film transport in micro evaporators and heat pipes are also discussed.

Efficient Treatment of Fixed and Induced Dipolar Interactions

2000 ◽  
Vol 653 ◽  
Author(s):  
Celeste Sagui ◽  
Thoma Darden
Keyword(s):  
Molecular Dynamics ◽  
Md Simulations ◽  
Lagrangian Formalism ◽  
Dipolar Interactions ◽  
Time Step ◽  
Efficient Treatment ◽  
Particle Mesh Ewald ◽  
Fixed Charges ◽  
Self Consistency ◽  
Induced Dipoles

AbstractFixed and induced point dipoles have been implemented in the Ewald and Particle-Mesh Ewald (PME) formalisms. During molecular dynamics (MD) the induced dipoles can be propagated along with the atomic positions either by interation to self-consistency at each time step, or by a Car-Parrinello (CP) technique using an extended Lagrangian formalism. The use of PME for electrostatics of fixed charges and induced dipoles together with a CP treatment of dipole propagation in MD simulations leads to a cost overhead of only 33% above that of MD simulations using standard PME with fixed charges, allowing the study of polarizability in largemacromolecular systems.

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