Effective Particle Size From Molecular Dynamics Simulations in Fluids
Abstract
Here, we report molecular dynamics simulations designed to investigate the effective size of colloidal particles suspended in a fluid in the vicinity of a rigid wall where all interactions are defined by smooth atomic potential functions. These simulations are used to assess how the behavior of this system at the atomistic length scale compares to continuum mechanics models. In order to determine the effective size of the particles, we calculate the solvent forces on spherical particles of different radii as a function of different positions near and overlapping with the atomistically defined wall and compare them to continuum models. This procedure also then determines the effective position of the wall. Our analysis is based solely on forces that the particles sense, ensuring selfconsistency of the method. The simulations were carried out using both Weeks–Chandler–Andersen and modified LennardJones (LJ) potentials to identify the different contributions of simple repulsion and van der Waals attractive forces. Upon correction for behavior arising the discreteness of the atomic system, the underlying continuum physics analysis appeared to be correct down to much less than the particle radius. For both particle types, the effective radius was found to be ~0.75σ, where σ defines the length scale ofmore »
 Authors:
 Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Mechanical Engineering
 Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
 Publication Date:
 Research Org.:
 Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
 Sponsoring Org.:
 USDOE
 OSTI Identifier:
 1411988
 Alternate Identifier(s):
 OSTI ID: 1415366
 Report Number(s):
 LAUR1428035
Journal ID: ISSN 09354964
 Grant/Contract Number:
 AC5206NA25396
 Resource Type:
 Journal Article: Published Article
 Journal Name:
 Theoretical and Computational Fluid Dynamics
 Additional Journal Information:
 Journal Name: Theoretical and Computational Fluid Dynamics; Journal ID: ISSN 09354964
 Publisher:
 Springer
 Country of Publication:
 United States
 Language:
 English
 Subject:
 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 42 ENGINEERING; Molecular dynamics; Colloids; Particle size; Hydrodynamic flow; Particlewall interactions
Citation Formats
Ju, Jianwei, Welch, Paul Michael Jr., Rasmussen, Kim Orskov, Redondo, Antonio, Vorobieff, Peter, and Kober, Edward Martin. Effective Particle Size From Molecular Dynamics Simulations in Fluids. United States: N. p., 2017.
Web. doi:10.1007/s0016201704500.
Ju, Jianwei, Welch, Paul Michael Jr., Rasmussen, Kim Orskov, Redondo, Antonio, Vorobieff, Peter, & Kober, Edward Martin. Effective Particle Size From Molecular Dynamics Simulations in Fluids. United States. doi:10.1007/s0016201704500.
Ju, Jianwei, Welch, Paul Michael Jr., Rasmussen, Kim Orskov, Redondo, Antonio, Vorobieff, Peter, and Kober, Edward Martin. 2017.
"Effective Particle Size From Molecular Dynamics Simulations in Fluids". United States.
doi:10.1007/s0016201704500.
@article{osti_1411988,
title = {Effective Particle Size From Molecular Dynamics Simulations in Fluids},
author = {Ju, Jianwei and Welch, Paul Michael Jr. and Rasmussen, Kim Orskov and Redondo, Antonio and Vorobieff, Peter and Kober, Edward Martin},
abstractNote = {Here, we report molecular dynamics simulations designed to investigate the effective size of colloidal particles suspended in a fluid in the vicinity of a rigid wall where all interactions are defined by smooth atomic potential functions. These simulations are used to assess how the behavior of this system at the atomistic length scale compares to continuum mechanics models. In order to determine the effective size of the particles, we calculate the solvent forces on spherical particles of different radii as a function of different positions near and overlapping with the atomistically defined wall and compare them to continuum models. This procedure also then determines the effective position of the wall. Our analysis is based solely on forces that the particles sense, ensuring selfconsistency of the method. The simulations were carried out using both Weeks–Chandler–Andersen and modified LennardJones (LJ) potentials to identify the different contributions of simple repulsion and van der Waals attractive forces. Upon correction for behavior arising the discreteness of the atomic system, the underlying continuum physics analysis appeared to be correct down to much less than the particle radius. For both particle types, the effective radius was found to be ~0.75σ, where σ defines the length scale of the force interaction (the LJ diameter). The effective “hydrodynamic” radii determined by this means are distinct from commonly assumed values of 0.5σ and 1.0σ, but agree with a value developed from the atomistic analysis of the viscosity of such systems.},
doi = {10.1007/s0016201704500},
journal = {Theoretical and Computational Fluid Dynamics},
number = ,
volume = ,
place = {United States},
year = 2017,
month =
}

Here, we report molecular dynamics simulations designed to investigate the effective size of colloidal particles suspended in a fluid in the vicinity of a rigid wall where all interactions are defined by smooth atomic potential functions. These simulations are used to assess how the behavior of this system at the atomistic length scale compares to continuum mechanics models. In order to determine the effective size of the particles, we calculate the solvent forces on spherical particles of different radii as a function of different positions near and overlapping with the atomistically defined wall and compare them to continuum models. Thismore »

Finitesize dependence of the bridge function extracted from molecular dynamics simulations
The bridge function for liquid sodium at T=373K is obtained by using the mean spherical approximation to extrapolate the pair distribution function (PDF), calculated in molecular dynamics (MD) simulations, beyond the half simulation box length for two sizes of the MD system. The bridge function is found to strongly depend on the total number of particles used in the simulation cell. This dependency leads to a spurious maximum of the static structure factor at long wavelengths, obtained from the reference hypernettedchain approximation (RHNC) with the MD system used as a reference system (RHNCMD). A simple selfconsistent procedure, proposed to accountmore »