%0 Journal Article
%T Influence of the Periodic Boundary Conditions on the Fluid Structure and on the Thermodynamic Properties Computed from the Molecular Simulations Influence des conditions p¨¦riodiques sur la structure et sur les propri¨¦t¨¦s thermodynamiques calcul¨¦es ¨¤ partir des simulations mol¨¦culaires
%A Jane£¿ek J.
%J Oil & Gas Science and Technology
%D 2013
%I Institut Fran?ais du P¨¦trole
%R 10.2516/ogst/2012037
%X The components of pair distribution function in different directions with respect to the coordinate system defined by the simulation box are determined for Lennard-Jones fluid simulated using the Monte Carlo technique in cubic boxes of various size. The approach of Pratt and Haan is employed to analyze the distortion of isotropic fluid structure due to the periodic boundary conditions and qualitative agreement is found between the theoretical and simulated course of particular angular components of distribution function. The relation between the anisotropy of correlation functions and the system size dependency of residual energy and compressibility factor is analyzed. The finite size effects become significantly pronounced in systems with size lower than 5 particle diameters, especially if the length of the box-edge is equal to a non-integer multiple of molecular diameter. With increasing temperature the implicit finite size effects on fluid structure as well as on the thermodynamic properties become less important. The primary cause of the structure deformation lies in the short-range interparticle correlations and the long-range interactions are not important; therefore, the implicit finite size effects influence all kinds of atomistic simulations, including those using the interactions of finite range and in the molecular dynamics simulations. However, at present the simulated systems are usually of sufficiently large size and ignoring the implicit finite size does not lead to serious problems, except for the determination of surface properties using the inhomogeneous simulations which are more sensitive to the lateral dimension of simulation box. Nous avons d¨¦termin¨¦ les contributions directionnelles de la fonction de distribution par paire du fluide de Lennard-Jones, par simulation mol¨¦culaire de Monte Carlo dans des bo tes cubiques de diff¨¦rentes tailles. L¡¯approche de Pratt et Haan est utilis¨¦e pour analyser la distorsion de la structure de fluide caus¨¦e par les conditions p¨¦riodiques; la th¨¦orie et les r¨¦sultats de simulation sont en bon accord. Nous avons ¨¦tudi¨¦ la relation entre l¡¯anisotropie des fonctions de corr¨¦lation et la d¨¦pendance vis-¨¤-vis de la taille du syst¨¨me de l¡¯¨¦nergie interne r¨¦siduelle et du facteur de compressibilit¨¦. Les effets de taille deviennent significatifs dans les syst¨¨mes dont la taille de la bo te est inf¨¦rieure ¨¤ 5 fois le diam¨¨tre des particules, en particulier si la longueur de la bo te est ¨¦gale ¨¤ un multiple non entier du diam¨¨tre mol¨¦culaire. Quand la temp¨¦rature augmente, les effets de taille sur la structur
%U http://dx.doi.org/10.2516/ogst/2012037