In this paper, we present a study of supercooled liquids interacting with theLennard Jones (LJ) potential and the corresponding purely repulsive(Weeks-Chandler-Andersen or WCA) potential, over a range of densities andtemperatures, in order to understand the origin of their different dynamics inspite of their structures being similar. Using the configurational entropy asthe thermodynamic marker via the Adam Gibbs (AG) relation, we show that thedifference in the dynamics of these two systems at low temperatures can beexplained from thermodynamics. At higher densities both the thermodynamical anddynamical difference between these model systems decrease, which isquantitatively demonstrated in this paper by calculating different parameters.The study also reveals the origin of the difference in pair entropy despite thesimilarity in the structure. Although the maximum difference in structure isobtained in the partial radial distribution function (rdf) of the B type ofparticles, the rdf of AA pairs and AB pairs give rise to the differences in theentropy and dynamics. This work supports the observation made in an earlierstudy (Phys. Rev. Lett.,\textbf {113}, 225701, 2014) and shows that they aregeneric in nature, independent of density.
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