title: Structure and transport of aqueous electrolytes: from simple halides to radionuclide ions.
abstract: Molecular simulations are used to compare the structure and dynamics of conventional and radioactive aqueous electrolytes: chloride solutions with sodium, potassium, cesium, calcium, and strontium. The study of Cs(+) and Sr(2+) is important because these radioactive ions can be extremely harmful and are often confused by living organisms for K(+) and Ca(2+), respectively. Na(+), Ca(2+), and Sr(2+) are strongly bonded to their hydration shell because of their large charge density. We find that the water molecules in the first hydration shell around Na(+) form hydrogen bonds between each other, whereas molecules in the first hydration shell around Ca(2+) and Sr(2+) predominantly form hydrogen bonds with water molecules in the second shell. In contrast to these three ions, K(+) and Cs(+) have low charge densities so that they are weakly bonded to their hydration shell. Overall, the structural differences between Ca(2+) and Sr(2+) are small, but the difference between their coordination numbers relative to their surface areas could potentially be used to separate these ions. Moreover, the different decays of the velocity-autocorrelation functions corresponding to these ions indicates that the difference in mass could be used to separate these cations. In this work, we also propose a new definition of the pairing time that is easy to calculate and of physical significance regardless of the problem at hand.
authors.affiliation: Institut Charles Gerhardt Montpellier, CNRS (UMR 5253), Université Montpellier 2, ENSCM, 8 rue de l'Ecole Normale, 34296 Montpellier Cedex 05, France.
authors.forename: Remco
authors.initials: R
authors.lastname: Hartkamp
authors.affiliation: Institut Charles Gerhardt Montpellier, CNRS (UMR 5253), Université Montpellier 2, ENSCM, 8 rue de l'Ecole Normale, 34296 Montpellier Cedex 05, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Coasne
mesh_terms: D002118:Calcium / Q000737:chemistry; D002586:Cesium / Q000737:chemistry; D002712:Chlorides / Q000737:chemistry; D003198:Computer Simulation; D006860:Hydrogen Bonding; D007477:Ions / Q000737:chemistry*; D008958:Models, Molecular; D011188:Potassium / Q000737:chemistry; D011868:Radioisotopes / Q000737:chemistry; D012492:Salts / Q000737:chemistry; D012964:Sodium / Q000737:chemistry; D013324:Strontium / Q000737:chemistry; D014783:Viscosity; D014867:Water / Q000737:chemistry*
chemical_list: D002712:Chlorides; D007477:Ions; D011868:Radioisotopes; D012492:Salts; D014867:Water; D002586:Cesium; D012964:Sodium; D011188:Potassium; D002118:Calcium; D013324:Strontium