A Computational Study of the Solvation Chemistry of Zr4+ Cation Vojislava Pophristic, Department of Chemistry & Biochemistry, University of the Sciences in Philadelphia, Philadelphia, PA 19104 Despite widespread applications of zirconium, the structure and dynamics of the polynuclear species resulting from Zr4+ solvation in aqueous solution are not well understood. Using a combination of ab initio molecular dynamics and quantum mechanical studies in gas-phase and aqueous solution, we have determined structures of the Zr4+ dimer and trimer species, and analyzed their aqueous solution dynamics. Ab initio molecular dynamics simulations indicate that the trimer exists in a “stacked” form (below), which undergoes an oscillatory movement of one monomer unit with respect to the other two. We postulate therefore that the trimer is a transient species in the process of higher polymer formation. The finding that this species might persist only on a short time scale upon its formation explains conflicting experimental reports on its existence. Our simulations show that the Zr4+ dimer, can exist in several forms with respect to the bridging groups. The eclipsed form (above, left) spontaneously converts into the staggered one (above, right) in the course of the simulation. The Zr2(OH)2(H2O)12]6+ form is stable in aqueous solution on a ps time scale. The linear trimer form is not stable in gas-phase.