Polarizability of the nitrate anion and its solvation at the air/water interface (original) (raw)
Related papers
Computational study of anion solvation in nitrobenzene
Chemical Physics Letters, 2007
The solvation of anions in nitrobenzene was investigated by the polarizable continuum model (PCM). The PCM was parameterized from structural information obtained by molecular dynamics simulations (MD) of anionic solutions in nitrobenzene. The parameterization was performed against experimental free energies of solvation for 22 anions containing H, C, N, O, F, S, Cl, Br, Se, and I atoms. The calculated Gibbs free energies of solvation present a mean absolute deviation from the experimental data of 2.4 kcal/mol. Hartree-Fock and DFT computations produce equivalent results.
The Journal of Chemical Physics, 2002
A hybrid quantum-classical computational algorithm, which couples a density functional Hamiltonian to a classical bath, is applied to investigate symmetry breaking and the vibrational spectrum of [NO3]− in aqueous clusters. The nitrate ion was modeled using density functional theory with a Gaussian basis set; two different force fields for the classical bath were investigated: the TIP4P-FQ fluctuating charge and the
Journal of Chemical Theory and Computation, 2015
We describe a computationally efficient molecular simulation methodology for calculating the concentration dependence of the chemical potentials of both solute and solvent in aqueous electrolyte solutions, based on simulations of the salt chemical potential alone. We use our approach to study the predictions for aqueous NaCl solutions at ambient conditions of these properties by the recently developed polarizable force fields (FFs) AH/BK3 of Kiss and Baranyai (
The Journal of Chemical Physics, 2010
We present molecular dynamics simulations of the liquid-vapor interface of 1M salt solutions of nonpolarizable NaCl, NaBr, and NaI in polarizable transferable intermolecular potential 4-point with charge dependent polarizability water ͓B. A. Bauer et al., J. Chem. Theory Comput. 5, 359 ͑2009͔͒; this water model accommodates increased solvent polarizability ͑relative to the condensed phase͒ in the interfacial and vapor regions. We employ fixed-charge ion models developed in conjunction with the TIP4P-QDP water model to reproduce ab initio ion-water binding energies and ion-water distances for isolated ion-water pairs. The transferability of these ion models to the condensed phase was validated with hydration free energies computed using thermodynamic integration ͑TI͒ and appropriate energy corrections. Density profiles of Cl − , Br − , and I − exhibit charge layering in the interfacial region; anions and cation interfacial probabilities show marked localization, with the anions penetrating further toward the vapor than the cations. Importantly, in none of the cases studied do anions favor the outermost regions of the interface; there is always an aqueous region between the anions and vapor phase. Observed interfacial charge layering is independent of the strength of anion-cation interactions as manifest in anion-cation contact ion pair peaks and solvent separated ion pair peaks; by artificially modulating the strength of anion-cation interactions ͑independent of their interactions with solvent͒, we find little dependence on charge layering particularly for the larger iodide anion. The present results reiterate the widely held view of the importance of solvent and ion polarizability in mediating specific anion surface segregation effects. Moreover, due to the higher parametrized polarizability of the TIP4P-QDP condensed phase ͕1.31 Å 3 for TIP4P-QDP versus 1.1 Å 3 ͑TIP4P-FQ͒ and 0.87 Å 3 ͑POL3͒ ͓Ponder and Case, Adv. Protein Chem. 66, 27 ͑2003͔͖͒ based on ab initio calculations of the condensed-phase polarizability reduction in liquid water, the present simulations highlight the role of water polarizability in inducing water molecular dipole moments parallel to the interface normal ͑and within the interfacial region͒ so as to favorably oppose the macrodipole generated by the separation of anion and cation charge. Since the TIP4P-QDP water polarizability approaches that of the experimental vapor phase value for water, the present results suggest a fundamental role of solvent polarizability in accommodating the large spatial dipole generated by the separation of ion charges. The present results draw further attention to the question of what exact value of condensed phase water polarizability to incorporate in classical polarizable water force fields.
The Journal of Chemical Physics, 2003
The hybrid molecular-continuum model for polar solvation considered in this paper combines the dielectric continuum approximation for treating fast electronic ͑inertialess͒ polarization effects and a molecular dynamics ͑MD͒ simulation for the slow ͑inertial͒ polarization component, including orientational and translational solvent modes. The inertial polarization is generated by average charge distributions of solvent particles, composed of permanent and induced ͑electronic͒ components. MD simulations are performed in a manner consistent with the choice of solvent and solute charges such that all electrostatic interactions are scaled by the factor 1/ ϱ , where ϱ is the optical dielectric permittivity. This approach yields an ensemble of equilibrium solvent configurations adjusted to the electric field created by a charged or strongly polar solute. The electrostatic solvent response field is found as the solution of the Poisson equation including both solute and explicit solvent charges, with accurate account of electrostatic boundary conditions at the surfaces separating spatial regions with different dielectric permittivities. Both equilibrium and nonequilibrium solvation effects can be studied by means of this model, and their inertial and inertialess contributions are naturally separated. The methodology for computation of charge transfer reorganization energies is developed and applied to a model two-site dipolar system in the SPC water solvent. Three types of charge transfer reactions are considered. The standard linear-response approach yields high accuracy for each particular reaction, but proves to be significantly in error when reorganization energies of different reactions were compared. This result has a purely molecular origin and is absent within a conventional continuum solvent model.
Journal of Computational Chemistry, 2011
The dynamic coupling between a polarizable protein force field and a particle-based implicit solvent model is described. The polarizable force field, TCPEp, developed recently to simulate protein systems, is characterized by a reduced number of polarizable sites, with a substantial gain in efficiency for an equal chemical accuracy. The Polarizable Pseudo-Particle (PPP) solvent model represents the macroscopic solvent polarization by induced dipoles placed on mobile Lennard-Jones pseudo-particles. The solvent-induced dipoles are sensitive to the solute electric field, but not to each other, so that the computational cost of solvent-solvent interactions is basically negligible. The solute and solvent induced dipoles are determined self-consistently and the equations of motion are solved using an efficient iterative multiple time step procedure. The solvation cost with respect to vacuum simulations is shown to decrease with solute size: the estimated multiplicative factor is 2.5 for a protein containing about 1000 atoms, and as low as 1.15 for 8000 atoms. The model is tested for six 20 ns molecular dynamics trajectories of a traditional benchmark system: the hydrated Bovine Pancreatic Trypsin Inhibitor (BPTI). Even though the TCPEp parameters have not been refined to be used with the solvent PPP model, we observe a good conservation of the BPTI structure along the trajectories. Moreover, our approach is able to provide a description of the protein solvation thermodynamic at the same accuracy as the standard Poisson-Boltzman continuum methods. It provides in addition a good description of the microscopic structural aspects concerning the solute/solvent interaction.
Theoretical Study of the Dissociation of Nitric Acid at a Model Aqueous Surface
The Journal of Physical Chemistry A, 2007
The issue of acid dissociation of nitric acid at an aqueous surface is relevant in various portions of the atmosphere in connection with ozone depletion. This proton-transfer reaction is studied here via electronic structure calculations at the HF/SBK+(d) level of theory on the HNO 3 ‚(H 2 O) 3 model reaction system embedded in clusters comprising 33, 40, 45, and 50 classical, polarizable waters with an increasing degree of solvation of the nitrate group. Free energy estimates for all the cases examined favor undissociated, molecular nitric acid over the 0-300 K temperature range, including that relevant for the upper troposphere, where it is connected to the issue of the mechanism of nitric acid uptake by water ice aerosols. The presence of molecular HNO 3 at 300 K at the surface is further supported by vibrational band assignments in good agreement with a very recent surface-sensitive vibrational spectroscopy study of diluted HNO 3 /H 2 O solutions.
Theoretical investigation of the dication of molecular nitrogen
The Journal of Physical Chemistry, 1986
Ab initio configurational interaction calculations of electronic states of the doubly charged cation N22t are presented and the results used to calculate the energies and predissociation lifetimes of all (u, J) levels of the quasi-bound states. A comprehensive analysis of known experimental and theoretical data has been carried out with discussion of the sources of error and complexity of the problems. From a theoretical standpoint, relative energies of the lower states of each symmetry are believed to be accurate to within 0.1-0.2 eV, though results for some of the higher states may be far less reliable. The problem is greatly complicated by mixing of states of radically different character, such as occur when bound chargepolarization states correlating with N2+ plus N cross those describing essentially Coulombic repulsion curves. It was thus not possible to obtain reliable results at internuclear separations greater than about 3-4 A. Notwithstanding deficiencies in both experiment and theory, it is shown that a consistent interpretation is possible within quoted accuracies of experimental data from appearance energies of N22t, Auger spectra, double-charge-transfer spectroscopy, high-resolution optical spectroscopy, and kinetic energy release associated with predissociation on a broad range of time scales. '[2+i3); 2-(2), II(4), A(3), '[3/0, 0/2, 2/2, 2/11 3.776 *(2), rmi 3[2-(2), w)i
The Journal of Physical Chemistry B, 2008
The effects of ion force field polarizability on the interfacial electrostatic properties of ~1 M aqueous solutions of NaCl, CsCl and NaI are investigated using molecular dynamics simulations employing both non-polarizable and Drude-polarizable ion sets. Differences in computed depthdependent orientational distributions, "permanent" and induced dipole and quadrupole moment profiles, and interfacial potentials are obtained for both ion sets to further elucidate how ion polarizability affects interfacial electrostatic properties among the various salts relative to pure water. We observe that the orientations and induced dipoles of water molecules are more strongly perturbed in the presence of polarizable ions via a stronger ionic double layer effect arising from greater charge separation. Both anions and cations exhibit enhanced induced dipole moments and strong z alignment in the vicinity of the Gibbs dividing surface (GDS) with the magnitude of the anion induced dipoles being nearly an order of magnitude larger than those of the cations and directed into the vapor phase. Depth-dependent profiles for the trace and zz components of the water molecular quadrupole moment tensors reveal 40% larger quadrupole moments in the bulk phase relative to the vapor mimicking a similar observed 40% increase in the average water dipole moment. Across the GDS, the water molecular quadrupole moments increase non-monotonically (in contrast to the water dipoles) and exhibit a locally reduced contribution just below the surface due to both orientational and polarization effects. Computed interfacial potentials for the nonpolarizable salts yield values 20 to 60 mV more positive than pure water and increase by an additional 30 to 100 mV when ion polarizability is included. A rigorous decomposition of the total interfacial potential into ion monopole, water and ion dipole, and water quadrupole components reveals that a very strong, positive ion monopole contribution is offset by negative contributions from all other potential sources. Water quadrupole components modulated by the water density contribute significantly to the observed interfacial potential increments and almost entirely explain observed differences in the interfacial potentials for the two chloride salts. By lumping all remaining non-quadrupole interfacial potential contributions into a single "effective" dipole potential, we observe that the ratio of quadrupole to "effective" dipole contributions range from 2:1 in CsCl to 1:1.5 in NaI suggesting that both contributions are comparably important in determining the interfacial potential increments. We also find that oscillations in the quadrupole potential in the double layer region are opposite in sign and partially cancel those of the "effective" dipole potential.