Now showing 1 - 10 of 21
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    Electron transfer reactions at metal electrodes: Influence of work function on free energy of activation and exchange current density
    (01-10-2001)
    Harinipriya, S.
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    An explicit expression for the exchange current density in terms of work function of the metal surface, surface potential of the reactants and products, and solvation energies was derived. The usefulness of the expression was demonstrated for a ferric/ferrous reaction whose i0 values have been reported for a variety of electrodes using experimental data and theoretical calculations.
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    Hardness of metals from electron transfer reactions at electrode surfaces
    (15-11-2002)
    Harinipriya, S.
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    A new parametric relation for hardness incorporating the surface potential of the metal and work function was derived. Hydrogen evolution and ferric/ferrous redox reactions were considered as examples to extract chemical hardness from electrode kinetic data.
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    Estimation of the activation energies for heterogeneous catalytic processes from thermodynamic and structural considerations
    (16-01-2004)
    Harinipriya, S.
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    The activation energies for three different heterogeneous catalytic processes is evaluated from phenomenogical thermodynamic considerations in conjunction with structural aspects inferred from various mechanistic sequences. The surface coverages of adsorbed species, lattice coordination number of single crystals and polycrystalline metals as well as the corresponding work functions are explicitly incorporated. The reactions considered are the synthesis of ammonia, decomposition of formic acid and hydrogenation of ethylene. The estimated activation energies for the synthesis of ammonia on Fe(111) and Ru(0001) surfaces show satisfactory agreement. In the case of formic acid decomposition, the volcano plot between the activation energy and reaction temperature is rationalized and the subtle role of work functions is indicated. The activation energy for the hydrogenation of ethylene on Pd(111) and Pt(111) is estimated and shown to be consistent with the experimental data. A simple phenomenological expression for the activation energy is shown to be valid for three different heterogeneous processes, viz. formation, decomposition and addition reactions. © 2003 Elsevier B.V. All rights reserved.
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    Analysis of electron transfer processes across liquid/liquid interfaces: Estimation of free energy of activation using diffuse boundary model
    (31-01-2006)
    Harinipriya, S.
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    The evaluation of the free energy of activation pertaining to the electron-transfer reactions occurring at liquid/liquid interfaces is carried out employing a diffuse boundary model. The interfacial solvation numbers are estimated using a lattice gas model under the quasichemical approximation. The standard reduction potentials of the redox couples, appropriate inner potential differences, dielectric permittivities, as well as the width of the interface are included in the analysis. The methodology is applied to the reaction between [Fe(CN)6]3-/4- and [Lu(biphthalocyanine)]3+/4+ at water/1,2-dichloroethane interface. The rate-determining step is inferred from the estimated free energy of activation for the constituent processes. The results indicate that the solvent shielding effect and the desolvation of the reactants at the interface play a central role in dictating the free energy of activation. The heterogeneous electron-transfer rate constant is evaluated from the molar reaction volume and the frequency factor. © 2006 American Chemical Society.
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    Estimation of de-deuteriation energies of lanthanum and uranium trihalides in heavy water
    (15-06-2006)
    Sudha, V.
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    Harinipriya, S.
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    The solvation energies of lanthanum and uranium trihalides in heavy water (D2O) are estimated by employing a novel simulation methodology in conjunction with statistical thermodynamic considerations incorporating random distribution of molecules, mean nearest neighbour distances and volume ratios. The deuteriation energies and the surface potentials at the solution/vacuum interface for UX3 and LaX3 (where X=F, Cl, Br and I) are estimated. The progressive manner in which de-deuteriation of UX3 and LaX3 molecules occurs has been computed and its importance is emphasized. © 2006 Elsevier B.V. All rights reserved.
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    Stability of scanning tunneling microscopy tip-induced bimetallic nanoclusters: Influence of hardness and composition on the cohesive energies
    (16-09-2004)
    Harinipriya, S.
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    The stability of bimetallic nanoclusters fabricated using scanning tunneling microscopy methods is investigated using a phenomenological formalism, and the cohesive energies of Au-Cu, Au-Pd, and Ag-Cu systems are estimated. The influence of chemical hardness, composition of the substrate, and metal adatoms in the nanocluster as well as the dissociation energies of S-S and S-M bonds as regards the stability of nanoclusters is demonstrated.
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    Hydration energies of trihalides of lanthanide and actinide series - A novel simulation methodology
    (10-09-2004)
    Sudha, V.
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    Harinipriya, S.
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    The apparent hydration energies of trihalides of Lanthanide and Actinide series are estimated incorporating mean nearest neighbour distances in conjunction with thermodynamic considerations. The estimated values are compared with those deduced using phenomenological versions. The formulation of hydration numbers of electrolytes at infinite dilution and at different concentrations is accomplished. The surface potentials of electrolytes at solution/vacuum interfaces are also computed. © 2004 Elsevier B.V. All rights reserved.
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    Dehydration energies of alkali metal halides. A new simulation methodology involving mean nearest neighbor distances and thermodynamic forces
    (02-03-2004)
    Harinipriya, S.
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    Sudha, V.
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    Dehydration energies of various alkali metal halides are estimated by employing a novel simulation methodology with the help of hydrated molecular radii. The hydration numbers at (i) infinite dilution and (ii) each movement of the molecules are calculated by employing random distribution of species in conjunction with ionic and molecular sizes. A satisfactory agreement with the reported estimates is noticed.
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    Analysis of electron transfer processes across liquid/liquid interfaces: Estimation of the equilibrium free energy of activation
    (05-02-2004)
    Harinipriya, S.
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    The equilibrium free energy of activation for electron-transfer processes across liquid/liquid interfaces is estimated using the desolvation energies, interfacial solvation numbers, and inner potential difference between the bulk and the interface for the ionic species and dielectric permittivities. The analysis employing a sharp boundary model is shown to yield a quantitative expression pertaining to the free energy of activation, solvent reorganization energy, and the rate constant. The methodology is applied to the electron transfer of [Fe(CN)6]3-/[Fe(CN)6]4- with (i) [Lu(biphthalocyanine)]4+/[Lu(biphthalocyanine)]3+ and (ii) TCNQ/TCNQ- redox couples in water/1,2 dichloroethane interface.
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    Influence of the work function on electron transfer processes at metals: Application to the hydrogen evolution reaction
    (09-07-2002)
    Harinipriya, S.
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    The exchange current density and the corresponding free energy of activation for the hydrogen evolution reaction at metal surfaces was analyzed using the work function of the substrate, desolvation energy of the reactant, solvation numbers. The electronic structure of metals was incorporated via their work function in the kinetics of heterogeneous electron-transfer reactions. The computed values were in satisfactory agreement with experimental data for a large number of metals.