AB-INITIO STUDY OF THE STABILIZATION OF MULTIPLY-CHARGED ANIONS IN WATER

Solvation effects on the geometries and electronic and thermodynamic s tabilities of a series of small multiply charged polyatomic anions, wh ich are not electronically and thermodynamically stable in the isolate d state, have been studied using the generalized conductor-like screen ing model of solvation. It was found that small doubly charged anions such as O2-, CO32-, and SO42- are electronically very stable in water with estimated vertical electron detachment energies as high as 6-7 eV . Even the triply charged (BO33-, PO43-, and MgF53-) and quadruply cha rged (MgF64-) anions are electronically stable in water. In the gas ph ase MgF42-, MgF53- and MgF64- are not stable toward loss of one F- ani on, but the doubly and triply charged anions were found to be thermody namically stable in water. Surprisingly, the aqueous electron detachme nt energies are not very strongly dependent on the charge of the anion , and the thermodynamic stabilities of singly, doubly, and triply char ged MgF(2+n)(n-) anions are very similar (as a result of which one can expect the coexistence of various charged anions in solutions and in melts).