• R Saravanan

      Articles written in Bulletin of Materials Science

    • Experimental 𝑓'' of As at 170, 200, 250 and 300 K from the Bijvoet pairs of GaAs

      G Raja Sudha K Vimala Devi D Arthi S Prasanna Subramanian N Srinivasan R Saravanan

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      Anomalous dispersion effects lead to the modification of the measured X-ray structure factors. In this work, we have determined the imaginary part of the anomalous dispersion correction terms (𝑓'' ) of arsenide atom (As), through the X-ray data collected using spherical single crystal of GaAs, at various temperatures, i.e. 170, 200, 250 and 300 K. It is stressed that more measurements of 𝑓'' of the elements are needed to confirm the theoretical calculations.

    • Optical, thermal and phase transition studies in Sn1–𝑥Ge𝑥Te

      M Sivabharathy N Sankar R Saravanan K Ramachandran

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      The optical and thermal properties of the mixed semiconducting alloy, Sn1–𝑥Ge𝑥Te, is studied by photo acoustics, for various Ge concentrations and phase transition for a particular concentration is also studied by the same method. The results are compared with the available literature values and discussed.

    • Electron density distribution and bonding in ZnSe and PbSe using maximum entropy method (MEM)

      K S Syed Ali R Saravanan S Israel R K Rajaram

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      The study of electronic structure of materials and bonding is an important part of material characterization. The maximum entropy method (MEM) is a powerful tool for deriving accurate electron density distribution in crystalline materials using experimental data. In this paper, the attention is focused on producing electron density distribution of ZnSe and PbSe using JCPDS X-ray powder diffraction data. The covalent/ionic nature of the bonding and the interaction between the atoms are clearly revealed by the MEM maps. The mid bond electron densities between atoms in these systems are found to be 0.544 e/Å3 and 0.261 e/Å3, respectively for ZnSe and PbSe. The bonding in these two systems has been studied using two-dimensional MEM electron density maps on the (100) and (110) planes, and the one-dimensional electron density profiles along [100], [110] and [111] directions. The thermal parameters of the individual atoms have also been reported in this work. The algorithm of the MEM procedure has been presented.

    • Analysis on insulator–metal transition in yttrium doped LSMO from electron density distribution

      S Israel S Saravana Kumar R Renuretson R A J R Sheeba R Saravanan

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      Yttrium doped LSMO (La1−𝑥Sr𝑥MnO3) was prepared using sol–gel technique and analysed for the insulator–metal transition fromcharge density variation in the unit cell with respect to different stoichiometric inclusion of yttrium. X-ray powder diffraction profiles of the samples were obtained and the well known Rietveld method and a versatile tool called maximum entropy method (MEM) were used for structural and profile refinement. The charge density in the unit cell was constructed using refined structure factors and was analysed. The charge ordering taking place in the insulator–metal transition was investigated and quantified. The insulator–metal transition was found to occur when 20% of La/Sr atoms were replaced by yttrium. The changes in the charge environment have also been analysed.

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