Exploration of Nanoscale Features of Thin Liquid Films on Solid Surfaces Using Molecular Dynamics Simulations

2004 ◽  
Author(s):  
Aaron P. Wemhoff ◽  
Van P. Carey
Keyword(s):  
Molecular Dynamics ◽  
Nucleate Boiling ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Solid Surfaces ◽  
Dynamics Simulation ◽  
Bulk Liquid ◽  
Metallic Surface ◽  
Interfacial Region ◽  
Far Field

Thin liquid films on solid surfaces are seen in a variety of systems including bubble growth during nucleate boiling and microgroove heat pipe evaporators and condensers. The small thickness of such films leads to difficult experimental observation of phenomena within various regions of the film: the wall-affected region, the bulk liquid, and the liquid-vapor interfacial region. A novel hybrid simulation methodology is used that combines a deterministic molecular dynamics simulation of the liquid regions with a stochastic treatment of the far-field vapor region boundary. In this simulation scheme, the imposed far-field pressure is iterated as the simulation is advanced in time until the mass in the system stabilizes at the specified temperature. This establishes the equilibrium saturation vapor pressure for the specified temperature as dictated by the intermolecular force interaction models for the fluid and molecules near the solid surface. Simulation results are presented for an argon liquid film on a metallic surface. The simulated surface tension values compare favorably with those from ASHRAE tables, although the simulated saturation density and pressure values behave as though the system is at a slightly higher temperature. The method presented here is a viable tool for simulating thin films on solid surfaces for systems operating far from the critical point.

Molecular-Level Modeling of Interfacial Phenomena: Use of Molecular Dynamics Simulations in Tandem With Statistical Thermodynamics Models

2007 ◽  
Author(s):  
Van P. Carey
Keyword(s):  
Molecular Dynamics ◽  
Md Simulation ◽  
Molecular Level ◽  
Md Simulations ◽  
Statistical Thermodynamics ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Interfacial Phenomena ◽  
Bulk Liquid ◽  
Interfacial Region

Nanoscale aspects of interfacial phenomena can be critically import in convective vaporization and condensation in nanochannels or microchannels. Molecular dynamics (MD) simulations have been extensively used to model and explore the physics of interfacial phenomena at the molecular level. Efforts to improve MD simulations have often focused on development of more physically realistic interaction potentials used to model intermolecular force interactions, or on development of more efficient computing strategies. An important, and often overlooked aspect of MD simulations is the role that theoretical models from statistical thermodynamics can play in MD simulations. This paper argues that use of alternate statistical thermodynamics models, and unconventional strategies for using them, can be effective ways of enhancing MD simulations. The advantages of these types of approaches are explored in the context of three recent MD simulation studies of interfacial region thermophysics that have made use of statistical thermodynamics theory in novel ways. Examples considered include studies of the interfacial region between bulk liquid and vapor phases, thin liquid films on solid surfaces, and stability free thin liquid films. These examples illustrate ways that MD simulations can be combined with other models to enhance computational efficiency or extract more information from the MD simulation results. Successful strategies for implementing these types of scheme are examined, and their general applicability is assessed.

Characterization of thin liquid films using molecular dynamics simulation

2002 ◽  
Vol 16 (11) ◽  
pp. 1477-1484 ◽  
Author(s):  
Jaeil Lee ◽  
Seungho Park ◽  
Ohmyoung Kwon ◽  
Young Ki Choi ◽  
Joon Sik Lee
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Dynamics Simulation

Heat Capacity of Nanoconfined Liquid: A Molecular Dynamics Simulation

2017 ◽  
Author(s):  
Rifat Mahmud ◽  
A. K. M. Monjur Morshed ◽  
Titan C. Paul
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Molecular Dynamics Simulation ◽  
Molar Heat Capacity ◽  
Molecular Model ◽  
Solid Surfaces ◽  
Dynamics Simulation ◽  
Bulk Liquid ◽  
Liquid Domain ◽  
Lennard Jones

Equilibrium molecular dynamics (EMD) simulations aiming to investigate the effect of confinement gap thickness on constant volume molar heat capacity (Cv) of the confined liquid in nanoscale have been carried out by simultaneously controlling the density and temperature of the liquid domain. Simplified Lennard-Jones (LJ) molecular model is used to model the system where the liquid is entrapped between two flat solid surfaces separated by a distance varying from 0.585 nm to 27.8 nm. Molar heat capacity of the bulk liquid has been evaluated using fluctuation formula which matches greatly with the NIST data and published literatures. But in case of confined liquid, molar heat capacity is observed to vary significantly with the gap thickness. For a specific range of gap thickness, molar heat capacity of the confined liquid is found higher than that of the bulk. But molar heat capacity of the nanogap confined liquid becomes independent of the gap thickness and approaches to that of the bulk liquid as gap thickness is greater than this specific range (6.14 nm for 100 K temperature of the confined liquid).

Dynamical Behavior and Flow Mechanism of Fluid in Nanochannel by Molecular Dynamics Simulation

2009 ◽  
Author(s):  
Juanfang Liu ◽  
Chao Liu ◽  
Qin Li
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Dynamical Behavior ◽  
Velocity Profiles ◽  
The Other ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Interfacial Region ◽  
Flow Mechanism ◽  
Bulk Fluid

The flow properties and dynamical behavior of fluid in a nanochannel were investigated by nonequilibrium molecular dynamics simulation. First of all, the locale distribution of molecules in the channel is found to be strongly inhomogeneous compared to the bulk fluid. In the vicinity of the wall, portion of the fluid molecules are absorbed on the surface of wall due to the strong interaction of the atoms between the wall and liquid, so that the fluid density in the contact region would be much larger than one of the bulk fluid. But in the other region, the local density value approaches one of the bulk fluids with the increasing distance from the wall. This oscillatory behavior of density resulted in different motion behavior of molecules in the different region of nanochannel. The molecular behavior in the interfacial region is remarkably different from those of fluid atoms in the center of channel and wall atoms, which posses both the motion properties of bulk liquids and a solid atom. At the molecular level, macroscopic continuum hypothesis failed, that is, the results predicted by the Navier-Stoke equations deviate from the simulation data adopted by molecular dynamics simulation. In the paper, the velocity profiles for the channels with different width were plotted, which demonstrated that the time-averaged velocity profiles was not quadratic when the channel width was less than 10 molecular diameters. But on the other cases, the velocity profiles will agree well with the analytical solution based on the NS theory. The molecular dynamics simulation method can withdraw the important microscopical information from the simulation process, which benefit to analyze the flow mechanism at such length scale channel.

MOLECULAR DYNAMICS SIMULATION OF PULSED LASER ABLATION

2011 ◽  
Vol 25 (04) ◽  
pp. 543-550 ◽  
Author(s):  
XIU-FANG GONG ◽  
GONG-XIAN YANG ◽  
PENG LI ◽  
YIN WANG ◽  
XI-JING NING
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Laser Pulses ◽  
Solid Surfaces ◽  
Dynamics Simulation ◽  
Angular Distributions ◽  
Adiabatic Expansion ◽  
Expansion Model

We have developed a simplified molecular-dynamical model for simulating ablation of solid surfaces by laser pulses, and specifically investigated expansion of Cu cloud in vacuum vaporized on the surface, showing that the angular distributions of the plume depend on the shape of the laser spot on the surface. In particular, experimentally observed flipover effects have been obtained, and an adiabatic constant determined from our simulations via an adiabatic expansion model agrees well with previous measurements.

Molecular dynamics simulation of geminal dicationic ionic liquids [Cn(mim)2][NTf2]2 – structural and dynamical properties

2018 ◽  
Vol 20 (1) ◽  
pp. 435-448 ◽  
Author(s):  
Majid Moosavi ◽  
Fatemeh Khashei ◽  
Elaheh Sedghamiz
Keyword(s):  
Molecular Dynamics ◽  
Ionic Liquids ◽  
Molecular Dynamics Simulation ◽  
Liquid Phase ◽  
Molecular Basis ◽  
Dynamics Simulation ◽  
Bulk Liquid ◽  
Fundamental Understanding ◽  
Dicationic Ionic Liquids ◽  
Dynamical Properties

The structural and dynamical properties of two dicationic ionic liquids, i.e. [Cn(mim)2][NTf2]2 with n = 3 and 5, have been studied to obtain a fundamental understanding of the molecular basis of the macroscopic and microscopic properties of the bulk liquid phase.

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