• Lakshman Pandey

      Articles written in Pramana – Journal of Physics

    • Study of electric potentials across a moving solid-liquid interface

      A K Bhuniya N Prasad Lakshman Pandey P Ramachandrarao

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      The electric potential across a melting sample of pure lead was measured as a function of time. A difference of the order of a few hundred microvolts was seen between the measured values of the potential and those calculated using the temperature gradients and the thermopowers of the solid and the liquid phases. This difference persists as long as the solid-liquid interface moves and is attributed to the Galvani potential present at the solid-liquid interface. It is suggested that such measurements can be used to obtain the value of the Fermi energy for liquids.

    • A stochastic model for solidification - I. The basic equations, their analysis and solution

      Shobha Dass Gautam Johri Lakshman Pandey

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      A 3-dimensional (2-space, 1-time) model relating the diffusion of heat and mass to the kinetic processes at the solid-liquid interface, using a stochastic approach is presented in this paper. This paper is divided in two parts. In the first part the basic set of equations describing solidification alongwith their analysis and solution are given. The process of solidification has a stochastic character and depends on the net probability of transfer of atoms from liquid to the solid phase. This has been modeled by a Markov process in which knowledge of the parameters at the initial time only is needed to evaluate the time evolution of the system. Solidification process is expressed in terms of four coupled equations, namely, the diffusion equations for heat and mass, the equations for concentration of the solid phase and for rate of growth of the solid-liquid interface. The position of the solid-liquid interface is represented with the help of a delta function and it is defined as the surface at which latent heat is evolved. A numerical method is used to solve the equations appearing in the model. In the second part the results i.e. the time evolution of the solid-liquid interface shape and its concentration, rate of growth and temperature are given.

    • A stochastic model for solidification II. Application to binary metallic melts

      Shobha Dass Gautam Johri Lakshman Pandey

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      A stochastic model to study the solidifcation process developed in part I is applied to various binary alloys having different values of interaction energies. The results obtained for the time evolution of temperature and concentration, rate of growth and shape of the solid-liquid interface are presented.

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