relations of the form where X ∗ are dimensionless transport properties with either macroscopic (Rosenfeld) or microscopic (Dzugutov) reduction parameters, s ∗ ex is the excess entropy per particle in units of k$_{B}$ . The scaling parameters, α and A , depend on the functional form of the underlying interactions. 20–26 In the case of simple liquids, the excess entropy scaling parameters can be approximately set as A ≈ 0 . 6 and α ≈ 0 . 8. In addition, for such fluids, the pair correlation entropy per particle, s ∗ $_{2}$, typically represents 85% to 90% of the total excess entropy. This paper focuses on the connection between the potential energy landscape (PEL) of a fluid and Rosenfeld excess entropy scaling of transport properties. Liquids in the stable, as opposed to the strongly supercooled regime, are characterized by a very high degree of connectivity between basins of local minima. This implies that the diffusivity, corresponding to the probability that a particle will make a successful move from its current position, will be proportional to the number of accessible configurational states, or exp( αs ∗ $_{ex}$). In order to develop a quantitative test of this intuitive picture, the diffusivity and/or the entropy must be correlated with landscape-based quantities that are sensitive to basin connectivity. We also require an energy landscape approach that does not presume a time-scale separation between intra- and inter-basin motions. An existing energy landscape approach that is simple to implement and satisfies these requirements is the Instantaneous Normal Mode (INM) approach. 37–39 In the INM approach, the key quantity is the ensemble-averaged curvature distribution of the PES sampled by the system. For a system of N particles, the mass- weighted Hessian associated with each instantaneous configuration is diagonalized to yield 3N normal mode eigenvalues and eigenvectors and the ensemble-average of this distribution is referred to as the INM spectrum. The short-time dynamics of the liquid can be derived from the INM spectra. Unlike in a crystalline solid, the INM spectrum of a liquid will have a substantial fraction of unstable modes with negative eigenvalues, corresponding to inter-basin crossing modes or shoulder regions within the same inherent structure basin. The diffusivity is strongly correlated with the properties of the INM spectrum, specially the fraction of imaginary frequencies, in both simple liquids, such as Lennard-Jones and Morse, 40–42 as well as molecular liquids, such as CS$_{2}$ and H$_{2}$O. 43–45 A refinement of the INM approach, shows that interbasin crossing or double-well modes are critical for diffusional motion. 46 3 X ∗ = A exp( αs ∗ $_{ex}$) , (3)