• N K Gaur

      Articles written in Pramana – Journal of Physics

    • HgO-added YBa2Cu3O7−δ superconductors

      Manglesh Dixit Shovit Bhattacharya Rajneesh Mohan Kiran Singh P S R Krishna Vilas Shelke N K Gaur R K Singh

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      The HgO-added YBa2Cu3O7−δ (YBCO) superconductor has been studied for its structural and superconducting properties. Polycrystalline YBCO samples were synthesized through solid-state reaction method by adding HgO in different concentrations without using oxygen annealing. All the samples showed a sharp superconducting transition temperature around 90 K. The X-ray diffraction patterns of all the samples revealed monophasic Y-123 nature. The structural studies were carried out by neutron scattering and Rietveld analysis. The neutron scattering revealed that Hg is not incorporated in the Y-123 system and has shown optimum oxygen concentration. The significant role played by the HgO is to provide oxygen ambient through its decomposition, thus changing the oxygen balance in favour of high Cu-valence state.

    • Static and dynamic properties of KCNxCl1−x

      Jyotsna Galgale Nupinder Kaur Preeti Singh Manik Manake N K Gaur R K Singh

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      An extended three-body force shell model (ETSM) has been applied to investigate the static and dynamic properties of KCNxCl1−x for the compositionx = 0.56 and 1.0 at 300 K. The phonon dispersion curves computed by us are compared with the single crystal neutron diffraction data. The unusual features of these curves are the upward curvature seen in some of the acoustic branches. This is a result ofK-dependent softening of the phonon due to translation-rotation coupling. The transverse acoustic branch is more soft near the zone centre.

    • Phonon dispersion curves of CsCN

      N K Gaur Preeti Singh E G Rini Jyotsna Galgale R K Singh

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      The motivation for the present work was gained from the recent publication on phonon dispersion curves (PDCs) of CsCN from the neutron scattering technique. We have applied the extended three-body force shell model (ETSM) by incorporating the effect of coupling between the translation modes and the orientation of cyanide molecules for the description of phonon dispersion curves of CsCN between the temperatures 195 and 295 K. Our results on PDCs in symmetric direction are in good agreement with the experimental data measured with inelastic neutron scattering technique.

    • Theoretical analysis of static properties of mixed ionic crystal: NH4Cl$_{1−x}$Br_{x}$

      D Rawat N K Gaur Sadhna Singh A Gour

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      In the present paper, we have investigated the static properties of the mixed ionic crystal NH4Cl$_{1−x}$Br$_{x}$ using three-body potential model (TBPM) by the application of Vegard’s law. The results for the mixed crystal counterparts are also in fair agreement with the pseudo-experimental data generated from the application of Vegard’s law. The results for the end point members ($x = 0$ and 1) are in good agreement with the experimental data. The results on compressibility, molecular force constant, infrared absorption frequencies and Debye temperature are presented probably for the first time for these mixed crystal counterparts.

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