• B L Tembe

      Articles written in Journal of Chemical Sciences

    • Solvent dynamics in a model system

      P Vijaya Kumar B L Tembe

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      We report herein a study of the solvent reorganization process in an electron transfer reaction. The calculations are based on a model consisting of 26 or 62 solvent particles. Molecular dynamics simulations are performed to calculate the electric field fluctuations during the orientational and translational motion of the solvent molecules. The changes in the electric fields at various points near the reacting sites in the system are evaluated as a function of time. From these electric fields, electric field time correlation functions are calculated. The main conclusion in this work is that it requires nearly 3 ps for the model solvent to reorient during the charge transfer. These results suggest ways of incorporating solvent dynamics based on molecular models into theoretical studies of electron transfer rates in condensed media.

    • SSOZ-HNC and SSOZ-PY integral equation studies of the structure of three-site polar fluids

      M Madhusoodanan C Satheesan Babu B L Tembe

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      Structure factors and site-site distribution functions for models of liquid carbon disulphide (CS2) and acetonitrile (CH3CN) are obtained by using the site-site Ornstein-Zernike (SSOZ) integral equation with the Percus-Yevick (PY) and the hypernetted chain (HNC) closures. The calculated structure factors are found to be in good agreement with the neutron and X-ray diffraction data as well as with the simulation data. The site charges have a significant effect on the distribution functions but not on the structure factors of both the systems. There is very good qualitative agreement between the calculated distribution functions and the results from computer simulations. Distinctive shoulders found in the simulation results for the first peaks of the C-N and CH3-CH3 distribution functions are enhanced in the calculations using the integral equations.

    • Temperature-dependence of time-dependent friction and electric field fluctuations

      K R Sivaprasad V Prasad K Manjula Devi B L Tembe

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      Molecular-dynamics simulations of a model dipolar system containing two ions have been carried out to study the effect of temperature on the time-dependent friction (ζ(t)) on the solute ions as well as the electric fields in the vicinity of the ions. It is found that with an increase in temperature, (i) the magnitude of ζ (0) increases and (ii) the electric field time correlation functions decay more rapidly at higher temperatures due to faster reorientations and translational diffusion of the molecules. The effects of the size of the system on these properties have also been investigated.

    • Potentials of mean force for the exo and endo solvolysis of 2-norbornyl chloride in water and DMSO: A constrained molecular dynamics study

      Subodh C Tiwari Timir Hajari Ashish Sharma B L Tembe

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      Constrained molecular dynamics is used to calculate the potentials of mean force for the exo and endo dissociation of 2-norbornyl chlorides in two solvents, namely water and dimethyl sulphoxide (DMSO). The gas phase potential energy curves for the 2-norbornyl chlorides are computed by ab initio methods and these curves are fitted into a 12-6-1 potential for use in classical molecular dynamics simulations. The gas phase potential energy curves indicate a greater barrier for the dissociation of the endo 2-norbornyl chloride (than the exo). The potentials of mean force (PMF) in DMSO and water indicate the locations and the magnitudes of the activation barriers in these solutions and are sensitive functions of the fitted gas phase potentials.

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