• B K Sharma

      Articles written in Pramana – Journal of Physics

    • Liquid fluorine properties by the hardsphere model with attractive interactions

      B K Sharma

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      We test the validity of an approximate equation of state of real fluids and the expression for surface tension of hardsphere liquids with attractive interactions derived by Sharma and others by obtaining expressions for isothermal compressibility,C1-parameter and acoustical parameter and relate them to microscopic Grüneisen parameter. The calculated values for liquid fluorine show fair agreement with experimental values.

    • Modified grüneisen and anderson-grüneisen relations for quasispherical molecular liquids

      B K Sharma

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      The validity of the expression for the Grüneisen parameter of liquids has been tested by obtaining expressions for the heat capacity ratio, isothermal and adiabatic Anderson-Grüneisen parameters,C1-parameter, Rao’s acoustical parameter, Beyer’s non-linearity parameter, and relate them to the Grüneisen parameter. The calculated values for five liquefied gases comparising of quasi-spherical molecules are reasonably satisfactory and explain the experimental results for the variation of heat capacity ratio, Beyer’s nonlinearity parameter andC1-parameter with temperature for liquid state. It is shown that the isochoric temperature derivative of the sound speed, specified heat ratio and the compressibility are dominant factors with significant contribution for influencing the thermo-acoustic properties of liquids.

    • Isochoric temperature coefficient of surface tension andSo-parameter of quasi-spherical molecular liquids

      B K Sharma

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      The Sharma parameterSo which is characteristic of molten alkali halides and polymers has also been shown to be characteristic of a wide variety of liquids. Calculated data using the volume expansivity of the liquid establish the constancy of theSo-parameter which retains, on an average, a constant value of 1·11 for quasi-spherical molecular liquids. It is shown thatSo-parameter is also related to volume expansivity of the surface layer of the liquid, temperature coefficient of surface tension of liquids and describes the temperature and volume or pressure dependence of thermodynamic Grüneisen parameter and isochoric heat capacity with significant contribution for influencing the thermoacoustic and surface tension properties of liquids.

    • Temperature invariance ofS0-parameter of polymers

      B K Sharma R R Reddy

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      The parameterS0 which is characteristic of molten alkali halides and liquids has also been shown to be characteristic of a wide variety of polymers. Calculated data using the volume expansivity of the polymer establish the temperature invariance and constancy of theS0-parameter which retains, on an average, a constant value of 1.11 for polymers. Further understanding of the significance of fractional free volume andS0-parameter in describing various thermoacoustic properties and the anharmonic behaviour in polymers, has been developed.

    • Renormalized-free-atom model and Compton profile of hcp cobalt

      B L Ahuja B K Sharma O Aikala

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      Compton profile of cobalt has been calculated employing the renormalized-free-atom model for fcc as well as hcp phases choosing several 3d-4s configurations. The results have been compared with recent gamma-ray measurements on polycrystalline Co. Best agreement between theory and experiment is found for 3d74s2 configuration. Comparison with free electron model has also been made for this case.

    • Compton profile study of α-manganese

      Anil Gupta B K Sharma B L Ahuja

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      The results of a Compton profile study on polycrystallineα-Mn are reported. Our measurement are compared with theoretical results computed for different 3d-4s electron configurations within the RFA model. Best agreement between the measured and calculated values is found for 3d5·44s1·6 configuration. Theoretical Compton profile ofγ-Mn calculated using the same procedure is close to that for bcc phase with similar electron configurations.

    • Relationship between the molecular constant, isothermal volume derivative of thermodynamic Grüneisen parameter, nonlinearity parameter and intermolecular forces in liquids

      B K Sharma

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      The isochoric temperature derivative of sound velocity, Beyer’s nonlinearity parameter, the isothermal volume derivatives of thermodynamic Grüneisen parameter and isochoric heat capacity and the repulsive exponent of intermolecular potential are shown to be related to the molecular constant representing the ratio of internal pressure to cohesive pressure of liquids. The calculated values are reasonably satisfactory and explain the experimental results on sound propagation data of liquids. The results have been used to develop further understanding of the significance of molecular constant, fractional free volume and repulsive exponent of intermolecular potential in describing various thermoacoustic and nonlinear properties and the anharmonic behaviour with regard to molecular order and intermolecular interactions in liquids.

    • Compton profile of molybdenum

      B K Sharma B L Ahuja Hanuman Singh F M Mohammad

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      In this paper we report the experimental Compton profile of polycrystalline molybdenum. The measurements have been made by scattering 59.54 keVγ-rays and are compared with the recent band structure calculation of Janiet al. [4]. These results have also been compared with our calculation based on the renormalized-free-atom model for different 4d-5s configurations. It is found that the present experimental data are relatively in good agreement with the band structure calculation.

    • A compton profile study of tantalum

      B K Sharma B L Ahuja Usha Mittal S Perkkiö T Paakkari S Manninen

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      We report the results of Compton profile study on polycrystalline tantalum. Measurements have been made using 59.54 keV gamma-rays. The results are compared with the APW band structure calculations of Papanicolaouet al and other available data. In contrast to the work of Changet al the overall agreement is better with the APW band structure which worsens on incorporating the electron correlation correction. Estimates of the errors due to the contribution from bremsstrahlung, non-validity of impulse-approximation and anomalous dispersion are also briefly discussed.

    • Electron momentum density distribution in iridium by Compton scattering technique

      K B Joshi R K Pandya B L Ahuja B K Sharma

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      The isotropic Compton profile of iridium, measured using 59.54 keVγ-rays, is reported in this paper. The results are compared with the theoretical Compton profiles from APW method with and without incorporating electron correlation effects. It is seen that correlation effects improve the agreement between the experiment and theory. Comparison with the renormalized-free-atom (RFA) model calculations has also been made. Behaviour ofd-band electrons in Ir and some other 5d transition metals is discussed in terms of broadening in their Compton profiles.

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