• Swapan K Ghosh

      Articles written in Journal of Chemical Sciences

    • Solvation forces in ionic and neutral liquids: A density functional approach

      Chandra N Patra Swapan K Ghosh

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      The solvation forces between two planar charged surfaces in ionic solutions, corresponding to charged and neutral hard spheres representing the ions and the solvent, respectively, are studied here using a weighted density functional theory for inhomogeneous Coulomb systems developed by us recently. The hard sphere contributions to the one-particle correlation function are evaluated nonperturbatively using a position-dependent effective density, while the electrical contributions are obtained through a perturbative expansion around this weighted density. The calculated results on the solvation forces between two charged hard walls compare well with available simulation results for ionic systems. For a neutral system, the present results show good agreement with the experimentally observed oscillating forces for two mica surfaces in octamethylcyclotetrasiloxane. The present approach thus provides a direct route to the calculation of interaction energies between colloidal particles.

    • A density functional theory-based chemical potential equalisation approach to molecular polarizability

      Amita Wadehra Swapan K Ghosh

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      The electron density changes in molecular systems in the presence of external electric fields are modeled for simplicity in terms of the induced charges and dipole moments at the individual atomic sites. A chemical potential equalisation scheme is proposed for the calculation of these quantities and hence the dipole polarizability within the framework of density functional theory based linear response theory. The resulting polarizability is expressed in terms of the contributions from individual atoms in the molecule. A few illustrative numerical calculations are shown to predict the molecular polarizabilities in good agreement with available results. The usefulness of the approach to the calculation of intermolecular interaction needed for computer simulation is highlighted.

    • Work distribution for a particle moving in an optical trap and non-Markovian bath

      Alok Samanta K Srinivasu Swapan K Ghosh

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      We propose a simple approach to derive an exact analytical expression of work distribution for a system consisting of a colloidal particle trapped in an optical harmonic potential well, which is being pulled at a constant velocity through a solution represented by a non-Markovian bath. The thermal environment is represented by a bath composed of an infinite set of harmonic oscillators, and a model Hamiltonian for the trapped colloidal particle is constructed by representing the interaction with the bathvia linear dissipative mechanism. We have studied the effects of pulling time, pulling speed, and the adiabatic limit. It is also observed that only at long time the total work is completely converted into dissipative work.

    • Computational investigation of hydrogen adsorption in silicon-lithium binary clusters

      Naresh K Jena K Srinivasu Swapan K Ghosh

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      Theoretical studies on hydrogen adsorption properties of silicon-lithium binary clusters are carried out. We have considered three different clusters viz., Si5Li$^{−5}$, Si5Li6 and Si5Li$^+_7$ and for each cluster, the geometries of different possible isomers are optimized. In all the minimum energy isomers of the three clusters considered, two of the lithium atoms are found to be situated in the axial positions and the remaining lithium atoms are in the equatorial position in the Si5 plane. The lithium atoms which are in Si5 plane are bonded to the Si-Si edge through a bridged bond instead of a corner in the Si5 ring. From the calculated atomic charges, it is found that there is a charge transfer from lithium to silicon leaving a partial positive charge on the Li atoms and the axial lithium atoms are more charged as compared to the remaining lithium atoms. In the case of Si5Li6 and Si5Li$^+_7$, the Li sites can trap a total of 14 and 17 H2 molecules, respectively, with each bridge bonded Li site adsorbing three H2 molecules and each axial Li adsorbing one H2 molecule which corresponds to a gravimetric density of 13.33 wt% and 15.25 wt%, respectively.

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