title: Diffusion maximum as a function of size in dense liquids.
abstract: We study the diffusion of small guest particles of different sizes in a host fluid at liquid densities using molecular dynamics simulations. We observe an enhancement of the diffusivity of guest particles for a size related to the structure of the void space of the host fluid, analogous to the "levitation effect" observed for guest diffusion in porous solids. Friction and activation energy are found to be minimum for the guest size with maximum self-diffusivity. Wavelength dependent self-diffusivity indicates a monotonic and oscillatory dependence on wave number k for anomalous and linear regimes, respectively. These are associated with single and bi-exponential decay of the incoherent intermediate scattering function.
authors.affiliation: Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India-560 012.
authors.forename: Pradip Kr
authors.initials: PK
authors.lastname: Ghorai
authors.forename: A V Anil
authors.initials: AV
authors.lastname: Kumar
authors.forename: Srikanth
authors.initials: S
authors.lastname: Sastry
authors.forename: S
authors.initials: S
authors.lastname: Yashonath