title: Aqueous Solvation of SmI2: A Born-Oppenheimer Molecular Dynamics Density Functional Theory Cluster Approach.
abstract: We report the results of Born-Oppenheimer molecular dynamics (BOMD) simulations on the aqueous solvation of the SmI2molecule at room temperature using the cluster microsolvation approach including 32 water molecules. The electronic structure calculations were done using the M062X hybrid exchange-correlation functional in conjunction with the 6-31G** basis sets for oxygen and hydrogen. For the iodine and samarium atoms the Stuttgart-Köln relativistic effective-core potentials were utilized with their associated valence basis sets. Starting from the optimized geometry of SmI2embeded in the microsolvation environment, we find a swift substitution of the iodine ions by eight tightly bound water molecules around Sm(II). Through the Sm-O radial distribution function and the evolution of the Sm-O distances, the present study predicts a first rigid Sm(II) solvation shell from 2.6 to 3.4 Å, whose integration leads to a coordination number of 8.4 water molecules, and a second softer solvation sphere from 3.5 to ca. 6 Å. The Sm(II)-O radial distribution function is in excellent agreement with that reported for Sr2+from EXAFS studies, a fact that can be explained because Sr2+and Sm2+have almost identical ionic radii (ca. 1.26 Å) and coordination numbers: 8 for Sr2+and 8.4 for Sm2+. The theoretical EXAFS spectrum was obtained from the BOMD trajectory and is discussed in the light of the experimental spectra for Sm(III). Once microsolvation is achieved, no water exchange events were found to occur around Sm2+, in agreement with the experimental data for Eu2+(which has a nearly identical charge-to-ionic radius relation as Sm2+), where the mean residence time of a water molecule in [Eu(H2O)8]2+is known to be ca. 230 ps.
authors.affiliation: Depto. de Física, Centro de Investigación en Ciencias-IICBA Universidad Autónoma del Estado de Morelos , Cuernavaca, Morelos 62209, México.
authors.forename: A
authors.identifier: http://orcid.org/0000-0002-8428-5714
authors.initials: A
authors.lastname: Ramı Rez-Solı S
authors.affiliation: Instituto de Ciencias Físicas, UNAM , Cuernavaca, Morelos 62210, México.
authors.forename: J I
authors.initials: JI
authors.lastname: Amaro-Estrada
authors.affiliation: Instituto de Ciencias Físicas, UNAM , Cuernavaca, Morelos 62210, México.
authors.forename: J
authors.initials: J
authors.lastname: Hernández-Cobos
authors.affiliation: Laboratoire de Physique et Chimie de Nano-objets, Université de Toulouse, INSA-CNRS-UPS , 135 Avenue de Rangueil, 31077 Toulouse, France.
authors.forename: L
authors.identifier: http://orcid.org/0000-0003-2653-8557
authors.initials: L
authors.lastname: Maron