Equilibrium fluctuations of liquid state static properties in a subvolume by molecular dynamics
Author(s)
Heyes, DM
Dini, D
Smith, ER
Type
Journal Article
Abstract
System property fluctuations increasingly dominate a physical process as the sampling volume decreases. The purpose of this work is to explore how the fluctuation statistics of various thermodynamic properties depend on the sampling volume, using molecular dynamics (MD) simulations. First an examination of various expressions for calculating the bulk pressure of a bulk liquid is made, which includes a decomposition of the virial expression into two terms, one of which is the Method of Planes (MOP) applied to the faces of the cubic simulation cell. Then an analysis is made of the fluctuations of local density, temperature, pressure, and shear stress as a function of sampling volume (SV). Cubic and spherical shaped SVs were used within a spatially homogeneous LJ liquid at a state point along the melting curve. It is shown that the MD-generated probability distribution functions (PDFs) of all of these properties are to a good approximation Gaussian even for SV containing only a few molecules (∼10), with the variances being inversely proportional to the SV volume, Ω. For small subvolumes the shear stress PDF fits better to a Gaussian than the pressure PDF. A new stochastic sampling technique to implement the volume averaging definition of the pressure tensor is presented, which is employed for cubic, spherical, thin cubic, and spherical shell SV. This method is more efficient for less symmetric SV shapes.
Date Issued
2016-09-13
Online Publication Date
2016-09-13
2016-09-21T09:14:29Z
Date Acceptance
2016-08-22
ISSN
1089-7690
Publisher
AIP Publishing
Journal / Book Title
Journal of Chemical Physics
Volume
145
Issue
10
Copyright Statement
© 2016 AIP Publishing LLC. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Journal of Chemical Physics and may be found at http://dx.doi.org/10.1063/1.4962165.
Source Database
pubmed
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (E
Engineering & Physical Science Research Council (EPSRC)
Grant Number
EP/G026114/1
EPSRC Fellowship Smith
EP/N025954/1
Subjects
Chemical Physics
02 Physical Sciences
03 Chemical Sciences
09 Engineering
Publication Status
Published
Article Number
104504