• D Roy

      Articles written in Pramana – Journal of Physics

    • An electron fluid model for the lattice dynamics of metals

      S K Das D Roy S Sengupta

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      An electron fluid model is proposed for the lattice dynamics of metals which satisfies the requirement of translational invariance and the lattice is in equilibrium without recourse to external forces. The model is applied to calculate the phonon dispersion of sodium in the symmetry directions.

    • Pseudopotential study of lattice parameter and heat of formation for substitutional alloys

      S K Das D Roy

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      Ashcroft’s empty core pseudopotential is applied to the substitutional alloy (K-CS) to calculate the heat of formation and lattice parameter over the entire concentration range. At any concentration the defect crystal is considered to be equivalent to a perfect crystal with a modified lattice parameter and the potential parameter for the defect crystal is calculated by using some suitable interpolation formula. The calculated results agree well with the available experimental results.

    • Scattering on energy-dependent separable potentials

      K Niyogi R N Panigrahi D Roy B Talukdar

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      We derive a coordinate space approach to energy-dependent separable potentials and clearly demonstrate its calculational advantage. The results presented include expressions for (i) low-energy scattering parameters and (ii) off-energy-shellT andK matrices. We study energy dependence of the effective potential with particular emphasis on cross-channel suppression effects.

    • A modified Ashcroft pseudopotential: application to aluminium

      S K Das D Roy S Sengupta

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      Unified study of the different properties of metals clearly reveals the inadequacy of the empty-core Ashcroft pseudopotential even in the case of simple metals. In the present paper we propose a modification of the one-parameter Ashcroft pseudopotential by assuming the parameterrc to be wave vector-dependent. This introduces a simple modification of the electron-ion pseudopotential in the reciprocal space. The corresponding potential in the configuration space shows that the abrupt change in the Coulomb potential atr=rc is replaced by a continuous change spread over a small region near the core boundary. The present model has been used to make a unified study of Al and is found to be a significant improvement over the simple Ashcroft model. The agreement between the calculated and experimental values is found to be quite satisfactory.

    • Unified study and transport properties of simple metals

      B Dutta D Dutta D Roy

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      The resistivity, thermoelectric power at the melting points and temperature variation of resistivity of the liquid alkali metals are studied with local Heine-Abarenkov and the modified Ashcroft pseudopotentials. The parameters of the model potentials are obtained from a unified study of the static and dynamic properties of the metals. The effect of different dielectric function and structure factor on the transport properties is discussed. It is shown that the simple modified Ashcroft pseudopotential reproduces the result fairly well except for Li and Cs.

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