M.V. Sangaranarayanan

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.

The dependence of underpotential deposition (UPD) shift on work function differences, lattice coordination numbers, solvent desorption energies, and surface coverages is analyzed. The transport processes that govern monolayer formation and bulk deposition are incorporated. The parameteric dependence of the UPD shift on different thermodynamic quantities and adsorbate charge densities is reported. The validity of the formalism is demonstrated by comparison with the experimental data.

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.

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.

Underpotential deposition (UPD) of metals is analysed from the perspective of phenomenological and statistical thermodynamic considerations; the parameters influencing the UPD shift have been quantitatively indicated using a general formalism. The manner in which the macroscopic properties pertaining to the depositing ions and solvent dipoles and the nature of the metallic substrate influence the UPD process are highlighted; earlier correlations of the UPD shift with the work function differences are rationalised. Anion-induced phase transitions which manifest as sharp peaks in experimental cyclic voltammograms are discussed using statistical thermodynamic models. © Indian Academy of Sciences.

The apparent dehydration energies and surface potentials of diverse alkaline earth halides are computed employing a novel simulation methodology incorporating hydration numbers, ion pairing effects and random distribution of molecules. The progressive variation of the hydration numbers and hydrated radii are estimated. The significance of the formalism in rationalizing the trend in the variation of the solubility, lattice energy, etc. is indicated. © 2004 Elsevier B.V. All rights reserved.

Grand Canonical Monte Carlo methods in conjunction with continuum Multiscale simulation to estimate the hydration energies and surface potentials of silver halides as demonstrated elsewhere is employed by incorporating random distribution of molecules, nearest neighbor distances and hydration numbers. The extent of dehydration during each step and the corresponding variation in the hydration numbers are evaluated, assuming the validity of hard spheres. These estimates are then employed to deduce the redox potential of the reaction viz. 2AgX(solution) ⇔ 2Ag(solid) + X2(gas). The dependence of these values on the nature of the halides and solvation characteristics is indicated.

Different techniques have been developed for enantiomeric separation in order to meet the need for optically pure materials in the pharmaceutical, fine chemical and electronic industries. The present study explores the extent of selective adsorption of chiral compounds on metal electrodes, from knowledge of adsorption energy difference between D- and L- enantiomers. An entirely new simulation strategy is employed via Monte-Carlo method to evaluate the adsorption energy difference between D- and L-enantiomers. This methodology also yields the amount of each species adsorbed for a chosen electrode potential. The adsorption of tetrameric D- and L- alanines at Cu, Ni and Zn electrodes as well as in solution are studied using their stabilization energies obtained atthe B3LYP/6-31G optimized structures. Subsequentlythese stabilization energies are employed as inputparameters to estimate the adsorption energy difference between D- and L-alanine tetramers. The adsorption energy difference obtained from the simulation is found to be identical with the umbrella inversion energy for the lone pair of electrons on the amino group. It is demonstrated that, in a racemic mixture, only the D-alanine tetramer gets adsorbed predominantly on Cu, Ni and Zn while the adsorption of the L-species is more facile than the D-form when the corresponding pure enantiomer is employed. The origin of the preferential adsorption of D-enantiomer from a racemic mixture is interpreted using the computation of the molar volumes of the optimized geometries. Thus the evaluation of the adsorption energy of chiral compounds on metal electrodes can lead to valuable predictions for separation of optically active pure enantiomers. © 2013, The Electrochemical Society, Inc. All rights reserved.

A simple simulation methodology to estimate the hydration energies and surface potentials of thallium halides is proposed, incorporating random distribution of molecules, nearest neighbor distances and hydration numbers. The extent of dehydration during each step and the corresponding variation in the hydration numbers are evaluated, assuming the validity of hard spheres. The correlation of the computed hydration energies with molecular sizes, lattice energies, crystal structures and feasibility of complexation reactions is discussed. © 2005 Elsevier B.V. All rights reserved.