Pair correlations in an NaCl-SPC water model

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Abstract
The ten pair correlation functions characterizing the equilibrium structure of a simple electrolyte such as NaCl-water and previously obtained for a NaCl-SPC water model within the extended RISM framework are tested against molecular dynamics, constrained dynamics and Monte Carlo simulations employing Ewald and reaction field schemes for a high-temperature, highpressure thermodynamic state where all these approaches become simultaneously feasible. The O-O, H-H, Cl-O, and Na-Na RISM correlations are in good agreement with the simulation data. The Na-O, Na-H, and Na-Cl results agree in phase, but the RISM peaks are too small. Distinct differences in the position of the first peak are observed in the case of the O-H, Cl-H, and Cl-Cl pair correlations. These results provide evidence that the main reason for these discrepancies are the statistical approximations involved in the extended RISM scheme.