Our interest lies in the collisional statistics in an arbitrary interacting fluid. We show that even in the low-density limit and contrary to naive expectation, the number of collisions experienced by a tagged particle in a given time does not obey Poisson law, and that, conversely, the free flight time distribution is not a simple exponential. As an illustration, the hard sphere fluid case is ...

We show how to effectively introduce a proper description of the velocity-changing collisions into the model of isolated molecular transition for the case of self- and Ar-perturbed H2. We demonstrate that the billiard-ball (BB) approximation of the H2-H2 and H2-Ar potentials gives an accurate description of the velocity-changing collisions. The BB model results are compared with ab initio class...

The role of forcing on the dynamics of a vertically shaken granular monolayer is investigated. Using a flat plate, surprising negative velocity correlations are measured. A mechanism for this anticorrelation is proposed with support from both experimental results and molecular dynamics simulations. Using a rough plate, velocity correlations are positive, and the velocity distribution evolves fr...

Classical trajectory (Monte Carlo) calculation is used to calculate collision rate constants of ion-quadrupolar molecule interactions for the H¯+C2H2 system. The method presented here takes into account the effect of the induced dipole-induced dipole potential on ion-quadrupolar molecule collision rate constants. It is also assumed that the colliding particles have a d...

We use observations of the radial profiles of the mass surface density of total, Σg, and molecular, ΣH2, gas, rotation velocity and star formation rate surface density, Σsfr, of the molecular dominated regions of 12 disk galaxies from Leroy et al. to test several star formation laws: a “Kennicutt power law”, Σsfr = AgΣ 1.5 g,2; a “Constant molecular law”, Σsfr = AH2ΣH2,2; the “Turbulence-regula...

We report a study of viscosity by the method of Helfand moment in systems with periodic boundary conditions. We propose a new definition of Helfand moment which takes into account the minimum image convention used in molecular dynamics with periodic boundary conditions. Our Helfand-moment method is equivalent to the method based on the Green-Kubo formula and is not affected by ambiguities due t...

We present one-dimensional molecular dynamics simulations of a two-species, initially uniform, freely evolving granular system. Colliding particles swap their relative position with a 50% probability allowing for the initial spatial ordering of the particles to evolve in time and frictional forces to operate. Unlike one-dimensional systems of identical particles, two-species one-dimensional sys...

Molecular configurations can be modeled as sets of spheres in 3D. By imposing geometric constraints on the spheres based on molecular biology one can apply efficient techniques [3], for example, to analyze the complexity of molecular surface [1]. Guibas et al. [2] introduced a model called necklace that finds applications in computer graphics, computer vision, robotics, geographic information s...

The aim of this work is to investigate argon scattering behaviors on the smooth and rough tungsten surfaces. Current work deals with numerical simulation of nanoscale heat transfer process accompanying with rarefied gas-solid substrate interactions using molecular dynamics (MD) method. Taking into account that this method is very time consuming, MD simulation using CUDA capable Graphic Cards is...

We study a three-dimensional model for driven granular media in which particles interact inelastically while they follow Brownian dynamics in between collisions. A steady Boltzmann-type kinetic equation associated with a pseudo-Maxwellian model is analyzed. Homogeneous steady states are found by a small inelasticity expansion. These states are given by a Maxwellian distribution corrected by the...