engleski

Water-like structure with repulsive double-core interactions

In this study, we show that a simple core-softened interaction, namely a soft-core 1/r12 interaction together with Gaussian repulsion, is able to reproduce the major features of radial distribution function and the structure factor of water, hence suggesting that such repulsive interaction is able to mimic the structure of real water [1]. We use both Monte Carlo simulations and the well known Percus-Yevick (PY) and Hypernetted-chain (HNC) integral equation theories. This study indicates that the structure of liquid water can be seen as the result of the two competing interactions, with two length scales: the diameter of the oxygen atom and the length of the hydrogen bond. It also indicates that this competition is not confined to near-neighbours, but is very (possibly infinitely) long ranged. It implies a very peculiar form of the density correlations and thus the cluster-structure of this particular liquid. This is indeed confirmed by the outcome of the integral equation studies. The HNC equation is able to reproduce the structure with puzzling accuracy -in view of its lesser accuracy when the Gaussian core is removed. In contrast, the PY equation has no solution for this state point ; it does at higher temperatures, but with dramatic inaccuracy, a result of its insufficient diagrammatic structure. These facts point to the intriguing nature of the density correlations in water, which remains -to date- largely unexplored. [1] A. Perera, A. Rispe, L. Zoranic, R. Mazighi and F. Sokolic, Molecular Physics, 107:13 (2009) 1349-1353

soft-core potential; integral equations; water

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