H. C. Gupta 《physica status solidi b》1990,159(2):K47-K49

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K. C. Jain  N. Gupta  N. S. Saxena 《physica status solidi b》1990,162(2):395-405

An effort is made to study the motion of effective atoms in liquid Na_0.5K_0.5 alloy in terms of velocity autocorrelation function, power spectrum, and mean square displacement analogous to the single particle motion in liquid metals employing the model developed by Glass and Rice in quasi crystalline approximation. The motions of effective atoms are also studied through the collective excitations by computing the longitudinal and transverse phonon frequencies. The results of collective excitations are in good agreement with the molecular dynamics (MD) results. Besides, results of thermodynamical properties such as isothermal bulk modulus and Debye temperature are also presented. The computed values are in good agreement with the results obtained by other theoretical calculations.  相似文献   

    

R. K. Puri  L. R. Gupta 《physica status solidi b》1977,83(1):293-298

Ratios of impurity-host to host-host spring force constants are computed from the temperature variation of recoilfree fraction and second order Doppler shift of Mössbauer Sn¹¹⁹ atoms present as dilute impurity in hosts of various masses. The weighted mean temperatures θ(−2), θ(−1), θ(+1), and θ(+2) of Mössbauer impurity atoms in various hosts are calculated from the temperature variation of recoilfree fraction and second order Doppler shift. Such calculations of force constant change for various impurity-host systems are made on the basis of nearest neighbour central forces model assuming Debye spectrum by taking account of relative weighting of resonance and localised modes of vibration. The computed results are interpreted to discuss how temperature, mass, and force constant changes would affect the Mössbauer parameters.  相似文献   

    

T. N. Agrawal  R. K. Gupta  G. L. Gupta 《physica status solidi b》1975,68(1):307-317

The applicability of Kihara's potential function to rare-gas solids has been investigated by studying their lattice dynamics. The intermolecular potential parameters are determined from the experimental sublimation energy and lattice spacing extrapolated to 0 °K, taking into account the zero point energy. These parameters are used to compute the theoretical phonon spectra for the solidified rare gases neon, argon, krypton, and xenon. The theoretical results are found to compare well with available experimental data.  相似文献   

    

N.N. Saxena  S.N. Gupta  R.G. Anihindi 《Journal of Physics and Chemistry of Solids》1974,35(10):1451-1452

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P. C. Gupta  K. Singh 《Optical and Quantum Electronics》1974,6(4):305-311

In this paper, the techniques of extended pulse stroboscopic holography and holographic subtraction have been applied to the study of periodic, non-sinusoidal vibrations represented by a Jacobian elliptic function. Fringe irradiance distribution in reconstructed images has been evaluated for the two cases. For this purpose we make use of an expression for the characteristic fringe function derived from considerations of the effect of motion on the coherence. It is shown that the above-mentioned techniques are more advantageous for the measurement of periodic, non-sinusoidal vibrations than in the case of pure sinusoidal vibrations.  相似文献   

    

I. J. Gupta  S. K. Trikha 《physica status solidi b》1978,87(2):513-516

An earlier theoretical result connecting the reduced thermal conductivity and reduced temperature of dielectrics is modified to deal with the cases where boundary as well as dislocation scattering simultaneously limit the phonon lifetime at low temperatures. Comparison with experimental data in case of solid argon and neon give satisfactory agreement for T* < 1.4.  相似文献   

    

I. J. Gupta  S. K. Trikha 《physica status solidi b》1978,88(2):815-818

The thermal conductivity of neon samples from 0.5 to 10 K is analysed on the basis of Holland's formulation. Fairly good agreement is found between the theoretical and the experimental results of Clemans. It is found for neon samples that longitudinal phonons carry only 15 to 30% of heat, as was shown for argon. The values of the dislocation densities and the average grain sizes of the polycrystalline neon samples are also determined.  相似文献   

    

K Datta  V K Gupta  N Panchapakesan  J N Passi  R P Saxena 《Pramana》1977,8(2):174-183

The measurements of the ΔI = 1 part of the parity violating nuclear force when combined with information on neutral current couplings from neutrino scattering and pion production experiments allow an estimate of the isoscalar admixture in the neutral current if it has a vector axial-vector structure has been shown.  相似文献   

    

O. P. Gupta  P. R. Wallace 《physica status solidi b》1972,54(1):53-60

We have devised a successive approximation scheme for taking account of the trigonal warping (γ₃) terms in the calculation of the lower-lying magnetic levels of graphite at fields ⩾ 20 kG. A two-component effective Hamiltonian has been introduced for these levels. Starting from analytic expressions in the case γ;₃ = 0, straightforward and simple iteration schemes have been devised (i) to take account of the higher levels and (ii) to obtain the γ₃ contributions. It is found that the trigonal warping changes the levels only by a few per cent except for the n = 0 levels. The levels n = 0, 1, 2, 3 have been calculated for a range of fields from 20 to 200 kG.  相似文献