Hydration shells of ions and ion pairs

Three-particle correlation functions

These pictures were obtained from molecular dynamics simulations of 1M NaCl aqueous solution (with flexible SRC water). Details of simulations see in papers

• A.P.Lyubartsev, A.Laaksonen, "Calculation of Effective Interaction Potentials from Radial Distribution Functions: A Reverse Monte Carlo Approach", Phys.Rev.E. v.52, p.3730 (1995) or
• A. P. Lyubartsev and A. Laaksonen "Concentration Effects in Aqueous NaCl Solutions. A Molecular Dynamics Simulation".. J.Phys.Chem., v.100 (40), p.16410-18 (1996)

The hydrated shells are displayed using three particle correlation functions (r₁,r₂,r₃). The distance between the first and second particles is fixed, usually it corresponds to a maximum of their RDF. Then one can construct distribution density of the third particle around fixed 1-st and 2-nd particle. On each of the following pictures you can see the densities of oxygens and hydrogens around two selected and fixed atoms. The color graphics allows one to display simultaneously the two densities using red color for oxygen and blue for hydrogens.

Hydration shells:

• Na+ (fixed Na-O at 2.37A)
• Cl- (fixed Cl-O at 3.21A)
• NaCl contact pair (fixed Na-Cl at 2.82A - first max. of NaCl RDF))
• NaCl solvent separated pair (fixed Na-Cl at 5.1A - second max of NaCl RDF)
• NaCl at 7A (third max of NaCl RDF)
• NaNa at 3.7A (first max of NaNa RDF)
• ClCl at 5.1A (first max of ClCl RDF)

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