MONTE CARLO SIMULATIONS OF Co (II) IN WATER INCLUDING THREE-BODY CORRECTION (original) (raw)

STRUCTURE OF Co(III) AND Fe(III) TRANSITION METAL IONS IN AQUEOUS SOLUTION

Bulletin of the Chemical Society of Ethiopia

The hydration structures of Co(III) and Fe(III) ions have been investigated by Metropolis Monte Carlo (MC) simulations using only ion-water pair interaction potentials and by including up to three body correction terms. The hydration structures were evaluated in terms of radial distribution functions, coordination numbers and angular distributions. The structural parameters obtained by including three-body correction terms are in good agreement with experimental values proving that many-body effects play a crucial role in the description of the hydration structure of these highly charged ions.

First Principles Simulations of the Structural and Dynamical Properties of Hydrated Metal Ions Me 2+ and Solvated Metal Carbonates (Me = Ca, Mg, and Sr)

Crystal Growth & Design, 2010

The structural and dynamical properties of the alkaline earth metal ions Mg 2þ , Ca 2þ , and Sr 2þ and their carbonate and bicarbonate complexes in aqueous solution are examined through first principles molecular dynamics simulations based on the density functional theory. Calculations were conducted in explicit heavy water molecules and at the average temperature of 400 K, conditions which are necessary to obtain a liquid-like water structure and diffusion time-scales when using gradient corrected density functionals. According to these simulations, the magnesium ion undergoes a significant contraction of its coordination sphere in the Mg(H)CO 3 (þ) aqueous complex, whereas calcium and strontium increase their average first shell coordination number when coordinated to HCO 3 or CO 3 2-

Classical and QM/MM molecular dynamics simulations of Co2+ in water

Chemical Physics, 2003

Classical and quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations have been performed to describe structural and dynamical properties of Co 2þ in water. The most important region, the first hydration shell, was treated by ab initio quantum mechanics at unrestricted Hartree-Fock (UHF) level using the LANL2DZ ECP basis set for Co 2þ and the double-f plus polarization basis set for water. For the rest of the system newly constructed three-body corrected potential functions were used. A well-structured rigid octahedron was observed for the stable first hydration shell showing no first shell water exchange process within a simulation time of 11.9 ps. For second hydration shell ligands, a mean residence time of 28 ps was observed. Librational and vibrational motions as well as the ion-oxygen motion were investigated by means of velocity autocorrelation functions showing significant differences between classical and QM/MM results.

Monte Carlo Simulation of Co 2+ in Aqueous Ammonia Solution Including Three-Body Correction Terms

Monte Carlo simulation have been performed in order to study the preferential Co 2+ solvation in waterammonia mixture. The simulation was done for a system consisting one Co 2+ in 4.76%, 10%, 18.6 % and 30% aqueous ammonia solution at temperature of 293.16 K, using ab initio three-body potentials for Co-H 2 O-H 2 O, Co-NH 3-NH 3 and Co-H 2 O-NH 3 interactions. The potentials were constructed at the Unrestricted Hartree-Fock (UHF) level using the basis sets of LANL2DZ/ECP for cobalt and 6-31G* from Gaussian 98 program for water and ammonia molecules. The experimental gas-phase geometry of the ammonia (N-H distance at 1.0124 Å and H-N-H angle of 106.67) and water (O-H distance of 0.9601 Å and H-O-H angle of 104.47 o) were kept rigid throughout the calculations. Result of the simulation can characterised the fully solvated of Co 2+ in 4.76%, 10%, 18.6 % and 30% aqueous ammonia solution as [Co(H 2 O) 6 ][H 2 O] 21 ] 2+ , [Co(H 2 O) 4 (NH 3) 2 ][(H 2 O) 18 ] 2+ , Co[(H 2 O) 2.9 (NH 3) 3.2 ] [(H 2 O) 10.4 (NH 3) 11.2 ] 2+ and [Co(H 2 O) 2 (NH 3) 4 ][(H 2 O) 5 (NH 3) 8 ] 2+. The structure of the solvated ion is discussed in terms of radial distribution functions and angular distributions which lead to the geometry structure of distortion octahedral for the first solvation shell.

Binding energies of hydrated cobalt hydroxide ion complexes: A guided ion beam and theoretical investigation

The Journal of Chemical Physics, 2017

The sequential bond energies of CoOH + (H 2 O) x complexes, where x = 1-4, are measured by threshold collision-induced dissociation using a guided ion beam tandem mass spectrometer. The primary dissociation pathway for all reactants consists of loss of a single water molecule. This is followed by the sequential loss of additional water molecules at higher collision energies for the x = 2-4 complexes, whereas the x = 1 reactant loses the OH ligand competitively with the H 2 O ligand. The kinetic energy dependent cross sections for dissociation of CoOH + (H 2 O) x complexes are modeled to obtain 0 and 298 K binding energies. Our experimental results agree well with theoretically determined bond dissociation energies (BDEs) at the B3LYP, B3LYP-GD3BJ, B3P86, and MP2(full) levels of theory with a 6-311+G(2d,2p) basis set using geometries and vibrational frequencies determined at the B3LYP/6-311+G(d,p) level. Thermochemical information for the loss of OH from CoOH + (H 2 O) x where x = 0-4 is also derived by combining the present experimental HO-Co + (H 2 O) and water loss BDEs from CoOH + (H 2 O) x with those for Co + (H 2 O) y from the literature. These BDEs are also compared to theory with mixed results.

Solvation and speciation of cobalt(II). A theoretical X-ray absorption and RIXS study

Chemical Physics, 2020

The X-ray spectroscopic signatures of solvated Co 2+ ions mimicking the aqueous solution of CoCl2 are investigated accounting for multiconfigurational as well as spin-orbit coupling effects. To this end the RASSCF/RASSI methodology with second order corrections due to dynamical correlation (RASPT2) is employed. Emphasis is put on the identification of spectral signatures of different species in octahedral, [Co(H2O)6-xClx] (2-x)+ , and tetrahedral, [Co(H2O)4-xClx] (2-x)+ , coordination. X-ray absorption spectra show distinct differences in the L3 band only. Here, the best agreement between theory and experiment is obtained for the hexaaqua complex [Co(H2O)6] 2+. For better identification of particular species it is proposed to use RIXS spectroscopy, which shows pronounced species-dependent inelastic features.

Molecular Theories and Simulation of Ions and Polar Molecules in Water

The Journal of Physical Chemistry A, 1998

Recent developments in molecular theories and simulation of ions and polar molecules in water are reviewed. The hydration of imidazole and imidazolium solutes is used to exemplify the theoretical issues. The treatment of long-ranged electrostatic interactions in simulations is discussed extensively. It is argued that the Ewald approach is an easy way to get correct hydration free energies in the thermodynamic limit from molecular calculations; and that molecular simulations with Ewald interactions and periodic boundary conditions can also be more efficient than many common alternatives. The Ewald treatment permits a conclusive extrapolation to infinite system size. Accurate results for well-defined models have permitted careful testing of simple theories of electrostatic hydration free energies, such as dielectric continuum models. The picture that emerges from such testing is that the most prominent failings of the simplest theories are associated with solvent proton conformations that lead to non-gaussian fluctuations of electrostatic potentials. Thus, the most favorable cases for second-order perturbation theories are monoatomic positive ions. For polar and anionic solutes, continuum or gaussian theories are less accurate. The appreciation of the specific deficiencies of those simple models have led to new concepts, multistate gaussian and quasi-chemical theories, that address the cases for which the simpler theories fail. It is argued that, relative to direct dielectric continuum treatments, the quasi-chemical theories provide a better theoretical organization for the computational study of the electronic structure of solution species.