content_image/335562.jpg
<img src='content_image/335562.jpg'>

of maximum diffusivity. Moreover, the region in which F$_{im}$ shows an anomalous increase with compression persists to very high temperatures, well above the temperature for onset of structurally anomalous behaviour. In order to understand this behaviour, we compare the zeroth, first and second derivatives of the potential as a function of pair separation with F$_{im}$ for T ∗ = 1 . 0 plotted as a function of the mean interparticle separation, ρ − 1 / 3 in Fig. (7). It is immediately obvious that the location of the minimum of F$_{im}$ coincides with the location of the minimum of the second derivative. For densities lower than this minimum, the second derivative increases and the number of imaginary modes decreases. Clearly, this effect persists in the high-temperature fluid where binary collisions dominate the dynamics since it reflects the curvature of the pair interaction. 

## V. INM SPECTRA AND LIQUID-STATE ENTROPY 

In section III, we discuss the possibility of partitioning the entropy of a liquid into con- tributions, S$_{r}$ and S$_{im}$ , associated with real and imaginary branches respectively of the INM spectrum. The S$_{r}$ contribution is directly derived from the frequency distribution of the 

