Integrated experimental and theoretical approach for the structural characterization of Hg2+ aqueous solutions

Abstract

The structural and dynamic properties of the solvated Hg2+ ion in aqueous solution have been investigated by a combined experimental-theoretical approach employing x-ray absorption spectroscopy and molecular dynamics (MD) simulations. This method allows one to perform a quantitative analysis of the x-ray absorption near-edge structure (XANES) spectra of ionic solutions using a proper description of the thermal and structural fluctuations. XANES spectra have been computed starting from the MD trajectory, without carrying out any minimization in the structural parameter space. The XANES experimental data are accurately reproduced by a first-shell heptacoordinated cluster only if the second hydration shell is included in the calculations. These results confirm at the same time the existence of a sevenfold first hydration shell for the Hg2+ ion in aqueous solution and the reliability of the potentials used in the MD simulations. The combination of MD and XANES is found to be very helpful to get important new insights into the quantitative estimation of structural properties of disordered systems.

A quantum mechanics, molecular dynamics and EXAFS investigation into the Hg2+ ion solvation properties in methanol solution

“…A combined MD, EXAFS and X-ray absorption near edge structure (XANES) investigation has revealed a quite unexpected sevenfold coordination for the Hg 2+ hydrated complex 8,54,55 , and the present results show that the solvation structure of Hg 2+ in water and methanol is similar, as it is characterized by similar first shell coordination numbers and distances (the position of the Hg-O g(r) first peak is 2.28Å in aqueous solution 8 ). A combined MD, EXAFS and X-ray absorption near edge structure (XANES) investigation has revealed a quite unexpected sevenfold coordination for the Hg 2+ hydrated complex 8,54,55 , and the present results show that the solvation structure of Hg 2+ in water and methanol is similar, as it is characterized by similar first shell coordination numbers and distances (the position of the Hg-O g(r) first peak is 2.28Å in aqueous solution 8 ).…”

How Does CeIII Nitrate Dissolve in a Protic Ionic Liquid? A Combined Molecular Dynamics and EXAFS Study

“…The EXAFS experimental data can be used to assess the validity of the Ce III coordination geometry obtained from the MD, and more generally, the reliability of the force field employed in the simulation . To this end χ( k ) theoretical signals have been calculated by introducing the Ce−O and Ce−N g ( r )′s obtained from the MD simulations into Equation (6).…”

Density functional theory based molecular dynamics study of hydration and electronic properties of aqueous La3+

“…2 where we show La-O and La-H RDF obtained from simulations using both PP1 and PP2. 10,[74][75][76] The role of counterions, at high concentration, on Ln͑III͒ solvation was found to be important and interesting by both theoretical 54,77,78 and experimental sides, 79 pointing out an important role when moving to concentrate solutions. The La-H RDF does not reach zero exactly-even if very small values are reached-since a hydrogen bonding network is established between first and second shell water molecules.…”