Diffusion of an impurity in the hard sphere fluid

✍ Scribed by T. Keyes

• Publisher: Elsevier Science
• Year: 1977
• Tongue: English
• Weight: 445 KB
• Volume: 51
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(77)80423-5

✦ Synopsis

The selfdiffusion coefficient (0) of a hard sphere of variable sire and mass, moving in a solvent of hard spheres of fved size and mass, is calculated in a version of the ring approximation (RA). It is found that (a) the ring contribution to D vanishes for particles smaller or less massive than the solvent, cb) D reaches a fmite limit, which varies with solvent density, as the tagged particle is made infinitely massive at fixed radius, and (c)D becomes infinite, and then negative, as the tagged particle radius is increased. The size and mass dependence of D in the RA is used as the basis of a criticism of the RA itself. It is argued that the repeated ring approximation is needed to provide a good theory for large, massive particles, and also, that "back-scattering" must be added to the RRA for pure fluids at high density.