Building a polarizable pair interaction potential for lanthanoids(III)in liquid water: A molecular dynamics study of structure and dynamicsof the whole series

摘要

In this work we have extended our previously presented polarizable pair interaction potential forLa~3+-water [Duvailet al.,J. Chem. Phys. 127, 034503 (2007)] to the whole lanthanoid(III) series(Ln~3+) interacting with water. This was performed taking into account known modification of ionicradius and atomic polarizability across the series and thus changing potential parameters accordingto that. Our procedure avoids the hard task of doing expensive high level ab initio calculations forall the atoms in the series and provides results in good agreement with experimental data and withab initio calculations performed on the last atom in the series (Lu~3+, the atom for which theextrapolation should be in principle much crude). Thus we have studied the hydration properties ofthe whole Ln~3+series by performing classical molecular dynamics in liquid phase. This systematicstudy allows us to rationalize from a microscopic point of view the different experimental results onLn~3+-water distances, first shell coordination numbers and first shell water self-exchange reactivity.In particular, we found that across the series the coordination number decreases from 9 for lightlanthanoids to 8 for heavy lanthanoids in a continuous shape. This is due to the continuous changingin relative stability of the two forms that can be both populated at finite temperature with differentprobabilities as a function of the Ln~3+atomic number. The changeover of the Ln~3+ionic radiusacross the series resulted to be the main driving physical properties governing not always theLn3+-water distance changing across the series but also the observed coordination number andconsequently ligand dynamics.