Ab initio studies on the chain of contact ion pairs of magnesium sulfate in supersaturated state of aqueous solution

In order to understand the formation of contact ion pairs as well as the chain of contact ion pairs detected by Raman technique in single supersaturated aqueous MgSO4 droplets levitated in an electrodynamic balance, ab initio method is used to optimize the geometry of several model units of the contact ion pairs. A series of contact ion model structures of monodentate and bidentate have been obtained on the basis of 6-31 + G*. Tetracooperated contact ions with chain structure for (MgSO4)(n) (n = 1, 2, 3, 4) as well as hexacooperated contact ions for (Mg2H(2)OSO(4))(n) (n = 1, 2, 3, 4) have also been optimized which is used to express the gel state of MgSO4 aqueous solution in supersaturated state. (C) 2002 Elsevier Science B.V. All rights reserved.