Structure and Dynamics of Hydrated Ag (I): Ab Initio Quantum Mechanical-Molecular Mechanical Molecular Dynamics Simulation (original) (raw)
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Ab Initio Molecular Orbital Computation Studies of Ag+-C2H4 Complexation in the Presence of Water
Ab initio calculations are done to explore the influence of water on the Ag + -C 2 H 4 complex formation. The simulated coordination environment of Ag ion is based on the existence of a dynamic equilibrium between the coordination of Ag ion with water and a sulfonate group, the counter ion. Calculated electronic properties reveal that electron delocalization from water molecules and the sulfonate group onto Ag 5s-atomic orbital reduces the ability of Ag ion to accept additional electrons from the C 2 H 4 π-orbital. The dissociation of water molecules from the hydrated Ag + is essential for the thermodynamic possibility of the Ag-C 2 H 4 complex formation. It is also evident from the electronic structure calculations that the dissociation of water is favorable for the formation of a stable Ag-C 2 H 4 complex. In the absence of water, the reaction between Ag ion strongly bound to sulfonate group and C 2 H 4 is thermodynamically impossible.
Orbital Computation Studies of Ag +-C 2 H 4 Complexation in the Presence of Water
2003
Ab initio calculations are done to explore the influence of water on the Ag-C2H4 complex formation. The simulated coordination environment of Ag ion is based on the existence of a dynamic equilibrium between the coordination of Ag ion with water and a sulfonate group, the counter ion. Calculated electronic properties reveal that electron delocalization from water molecules and the sulfonate group onto Ag 5s-atomic orbital reduces the ability of Ag ion to accept additional electrons from the C2H4 π–orbital. The dissociation of water molecules from the hydrated Ag is essential for the thermodynamic possibility of the Ag-C2H4 complex formation. It is also evident from the electronic structure calculations that the dissociation of water is favorable for the formation of a stable Ag-C2H4 complex. In the absence of water, the reaction between Ag ion strongly bound to sulfonate group and C2H4 is thermodynamically impossible.
Theoretical Investigation of Hydrated Hydronium Ions on Ag(111
We investigated the adsorption of hydronium ions on Ag(111) in conditions that simulate the structure of the double layer using the ab initio quantum mechanical Moller-Plesset second-order method. The most representative points of the potential energy surface for bare hydronium on Ag(111) were first investigated. Then, the ion was hydrated with 1, 2, and 3 water molecules, and the structures of the hydronium-water complexes were studied on Ag(111) under different externally applied homogeneous electric fields. Bare hydronium adsorbs via the hydrogen atoms with C 3V or C s symmetry. For these coordinations, the potential energy surface has a small corrugation: the binding energy on the hcp hollow site (-56 kcal/mol) is only 2 kcal/mol more stable than on the ontop site. On the other hand, adsorption via the oxygen atom is destabilized due to the Pauli repulsion with the metal. The equilibrium geometry of the trihydrated complex (H 9 O 4 + ) has the water molecules located between the hydronium ion and the surface, indicating that hydronium does not specifically adsorb. The surface reaction leading to H 9 O 4 + from adsorbed water and hydronium is very exothermic (-32 kcal/mol) mainly due to the formation of hydrogen bonds. The electric field has a smaller influence on the adsorption of the hydrated ion than on the bare ion due to the screening of the water molecules. The different contributions to the binding energy in the presence of electric fields were considered. The polarization contribution is more important for H 9 O 4 + than for H 3 O + and leads to a stabilization of the trihydrated complex at small positive electric fields.
Indonesian Journal of Chemistry and Environment, 2022
The structure and hydration dynamics of Ga3+ ion have been studied using classical Molecular Dynamics (MD) simulations. The data collection procedure includes determining the best base set, constructing 2-body and 3-body potential equations, classical molecular dynamics simulations based on 2-body potentials, classical molecular dynamics simulations based on 2-body + 3 potential-body. The trajectory file data analysis was done to obtain structural properties parameters such as RDF, CND, ADF, and dynamic properties, namely the movement of H2O ligands between hydrations shells. The results of the research indicated that the hydration complex structure of Ga(H2O)83+ and Ga(H2O)63+ was observed in molecular dynamics simulations (MM-2 body) and (MM-2 body + 3-body), respectively. The movement of H2O ligands occurs between the first and second shell or vice versa in the MD simulation of MM-2 bodies but does not occur in MD simulations of (MM-2 bodies + MM-3 bodies). Therefore, the wat...
Density functional theory study of the interaction of monomeric water with the Ag(111) surface
Ab initio density-functional theory has been used to investigate the adsorption of a single H 2 O molecule on the Ag͕111͖ surface. A series of geometry optimizations on a slab model has allowed us to identify a preferred energy minimum and several stationary points in the potential-energy surface of this system. The most stable adsorption position for water corresponds to the atop site, with the dipole moment of the molecule oriented nearly parallel to the surface. The electronic structure of several H 2 O-Ag clusters has been compared to results obtained by the extended slab calculations. The agreement found for several properties ͑binding energy, tilt angle of the dipole moment of water, and interatomic distances͒ provides evidence for the local nature of the water-metal atop interaction. The covalent contribution to the weak H 2 O-Ag bond is found to be an important one.
Molecular Physics, 2014
Molecular dynamics (Born-Oppenheimer) simulations based on density functional theory have been carried out to investigate the solvation structure of monovalent Na + and K + cations in water under ambient conditions. Four recently proposed van der Waals (vdW) density functionals (LMKLL, DRSLL, DRSLL-PBE, DRSLL-optB88), the semiempirical vdW method of Grimme (BLYP-D3) and conventional gradient-corrected (GGA-BLYP) density functionals are applied in order to evaluate their accuracy in describing the hydration structure of alkali metal ions. Theoretical results are compared to available experimental data. Our results indicate that addition of corrections accounting for dispersion forces significantly improves the agreement between predicted and measured coordination numbers for both Na + and K + cations. Analysis of radial distribution functions brings further support to the notion that the choice of the generalised gradient approximation density functional impacts crucially on the computed structural properties. DRSLL-optB88 and BLYP-D3 provide the best agreement with experiment.
The Journal of Chemical Physics, 2018
Full-dimensional vibrational spectra are calculated for both X − (H 2 O) and X − (D 2 O) dimers (X = F, Cl, Br, I) at the quantum-mechanical level. The calculations are carried out on two sets of recently developed potential energy functions (PEFs), namely TTM-nrg and MB-nrg, using the symmetry-adapted Lanczos algorithm with a product basis set including all six vibrational coordinates. Although both TTM-nrg and MB-nrg PEFs are derived from CCSD(T)-F12 data obtained in the complete basis set limit, they differ in how many-body effects are represented at short range. Specifically, while both models describe long-range interactions through the combination of two-body dispersion and many-body classical electrostatics, the relatively simple Born-Mayer functions employed in the TTM-nrg PEFs to represent short-range interactions are replaced in the MB-nrg PEFs by permutationally invariant polynomials to achieve chemical accuracy. For all dimers, the MB-nrg vibrational spectra are in close agreement with the available experimental data, correctly reproducing anharmonic and nuclear quantum effects. In contrast, the vibrational frequencies calculated with the TTM-nrg PEFs exhibit significant deviations from the experimental values. The comparison between the TTM-nrg and MB-nrg results thus reinforces the notion that an accurate representation of both short-range interactions associated with electron density overlap and long-range many-body electrostatic interactions is necessary for a correct description of hydration phenomena at the molecular level.
Chemical Physics Letters, 2004
The hydration of Fe 2þ and Fe 3þ ions in aqueous solution was studied by molecular dynamics simulation using ab initio pairwise interactions potential plus three-body correction terms. The simulations were performed at 298.16 K using the CF2 flexible water model. Radial distribution functions and their integration for Fe nþ-O show that six water molecules reside in the first hydration shell for both Fe 2þ and Fe 3þ ions, with R FeO being 2.15 and 2.05 A, respectively. The second hydration shell contains about 13 and 15 water molecules for Fe 2þ and Fe 3þ ions, respectively, forming hydrogen bonds to the water molecules in the first shell. Water exchange between the second shell and bulk occurs frequently. Librational and vibrational spectra of second shell water molecules are almost identical to those in the bulk, whereas for first shell ligands remarkable differences are observed.
Structure and dynamics of hydrated NH4+: Anab initio QM/MM molecular dynamics simulation
Journal of Computational Chemistry, 2005
A combined ab initio quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulation has been performed to investigate solvation structure and dynamics of NH 4 ϩ in water. The most interesting region, the sphere includes an ammonium ion and its first hydration shell, was treated at the Hartree-Fock level using DZV basis set, while the rest of the system was described by classical pair potentials. On the basis of detailed QM/MM simulation results, the solvation structure of NH 4 ϩ is rather flexible, in which many water molecules are cooperatively involved in the solvation shell of the ion. Of particular interest, the QM/MM results show fast translation and rotation of NH 4 ϩ in water. This phenomenon has resulted from multiple coordination, which drives the NH 4 ϩ to translate and rotate quite freely within its surrounding water molecules. In addition, a "structure-breaking" behavior of the NH 4 ϩ is well reflected by the detailed analysis on the water exchange process and the mean residence times of water molecules surrounding the ion.