• Concentration dependence of the mixed crystal modes of vibration

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    • Keywords


      Impurity modes; mixed crystals; lattice dynamics; coherent potential approximation

    • Abstract


      The concentration dependence of the reststrahl absorption in various mixed crystals exhibiting one, two and mixed mode behaviour is investigated using the coherent potential approximation (cpa). The phonon Green’s function, the impurity mode frequencies and the strength of absorption are calculated in the Einstein model from the generalizedcpa proposed by Tripathi and Behera which takes into account both mass and force constant changes. The introduction of a phenomenological concentration dependence of the force constant change parameter is shown to provide a satisfactory explanation of the concentration dependence of the experimental data for the twenty mixed crystal systems analysed. It is conjectured that the nearest neighbour force constant of an impurity atom substituted at a host site is very much different from that of a perfect crystal consisting of these impurity atoms and that both these play an important role in determining the one, two and mixed mode behaviour of the mixed crystals.

    • Author Affiliations


      P Nayak1 2 S N Behera1

      1. Institute of Physics, Bhubaneswar - 751 007, India
      2. Post-Graduate Department of Physics, G M College, Sambalpur - 768 004, India
    • Dates

  • Pramana – Journal of Physics | News

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      Posted on July 25, 2019

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