Test of Universal Scaling Law for Molecular Diffusion of Liquids in Bulk and Nanotube Confinement

The task of observing and understanding the relationship between transport and thermodynamic properties of atomic and molecular fluids has been a continuing open problem in condensed matter. The problem becomes more complex and challenging when the fluids are confined in nanoscale dimensions. In order to address this complex problem, a scaling law has been established by linking the molecular diffusivity and excess entropy of molecular liquids and liquid mixtures both in bulk and under nanoconfinement, which is found to be quite universal and also reproduces the earlier scaling law for atomic diffusion [Nature (London) 1996, 381, 137]. The excess entropy, which is central to this universal scaling law, has been estimated using a robust and very fast “two phase thermodynamic” (2PT) method, where density of states (DOS) has been employed, which may also be obtained from power spectrum of diffusing liquids using scattering experiments thus offers an indirect route to determine the molecular diffusivity. The ...