title: Effect of the computational domain size and shape on the self-diffusion coefficient in a Lennard-Jones liquid.
abstract: In the present study, molecular dynamics (MD) simulations on the monatomic Lennard-Jones liquid in a periodic boundary system were performed in order to elucidate the effect of the computational domain size and shape on the self-diffusion coefficient measured by the system. So far, the system size dependence in cubic computational domains has been intensively investigated and these studies showed that the diffusion coefficient depends linearly on the inverse of the system size, which is theoretically predicted based on the hydrodynamic interaction. We examined the system size effect not only in the cubic cell systems but also in rectangular cell systems which were created by changing one side length of the cubic cell with the system density kept constant. As a result, the diffusion coefficient in the direction perpendicular to the long side of the rectangular cell significantly increases more or less linearly with the side length. On the other hand, the diffusion coefficient in the direction along the long side is almost constant or slightly decreases. Consequently, anisotropy of the diffusion coefficient emerges in a rectangular cell with periodic boundary conditions even in a bulk liquid simulation. This unexpected result is of critical importance because rectangular fluid systems confined in nanospace, which are present in realistic nanoscale technologies, have been widely studied in recent MD simulations. In order to elucidate the underlying mechanism for this serious system shape effect on the diffusion property, the correlation structures of particle velocities were examined.
authors.affiliation: Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Gota
authors.initials: G
authors.lastname: Kikugawa
authors.affiliation: School of Engineering, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Shotaro
authors.initials: S
authors.lastname: Ando
authors.affiliation: School of Engineering, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Jo
authors.initials: J
authors.lastname: Suzuki
authors.affiliation: Graduate School of Engineering, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Naruke
authors.affiliation: Tokyo Electron Ltd., 17 Miyukigaoka, Tsukuba-shi, Ibaraki 305-0841, Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Nakano
authors.affiliation: Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Ohara
mesh_terms: D004058:Diffusion; D057446:Hydrodynamics; D056004:Molecular Dynamics Simulation