• Volume 30, Issue 5

May 1988,   pages  1-442

• Indications of superconductivity in the 200–300K range in the Bi-Ca-Sr-Cu-O system

Some of the Bi-Ca-Sr-Cu-O compositions show indications of onset of superconductivity in the 200–300 K region, possibly due to the intergrowth of different layered sequences.

• Circular orbits of an electron around a proton in Schwarzschild geometry

The energy of an electron in circular orbits around a proton in Schwarzschild geometry has been investigated and is found to be red shifted. The electrical dipole moment of such a system is also estimated.

• Non-statistical structures in12C(15N,4He)23Na reaction

The data on theϑlab=7° excitation functions of12C(15N,4He)23Na reaction betweenEcm=9.42 and 17.33 MeV for 28 states upto an excitation energy of 8.940 MeV in23Na have been subjected to statistical analysis. In addition to statistical fluctuations, the results of the analysis indicate the existence of non-statistical structures atEcm=10.66, 10.93, 11.38, 12.62, 13.16, 15.32 and 16.18 MeV.

• The minimax technique in relativistic Hartree-Fock calculations

Using the set of trial spinors$$\left\{ {N_i \left( {_{\hat \Omega _i u_i }^{u_i } } \right), i = 1, \ldots , N} \right\}$$ and the Dirac-Coulomb Hamiltonian (HDC) we discuss the role of the minimax theorem in relativistic Hartree-Fock calculations. In principle, the minimax theorem guarantees the occurrence of an upper bound. We also consider a scaling of the functionsui and discuss the condition to derive the relativistic hypervirial theorem; the variational procedure represented by the condition serves as an example of the minimax technique. Single zeta calculations onH2+,H2 and He are analysed. The effect of enlarging the basis is investigated for the He atom. The “upper bound” obtained by usingcoherent basis spinors differs from the result of the (random) linear variation using the kinetically balanced basis set by an amount which is at most of orderc−4. Use of thecoherent basis set is advocated.

• Temperature variation of the Debye-Waller factors of metal and halide ions in CsCl-Br solid solutions between room temperature and 90°K by powder X-ray diffraction

Solid solutions of CsCl-Br in different molal concentrations were prepared and X-ray diffractograms taken. The integrated intensities of the Bragg peaks have been estimated and structure factors were obtained. The crystal lattice in each of these solid solution samples is made up of a random distribution of Cs+, Cl and Br ions depending upon the molal concentration. A pseudo-atom model has been proposed in which the Cs+ ions occupy (000) position and a pseudo-atom occupies (1/2 1/2 1/2) position. The presence of incoherence scattering in these solid solutions has been considered by applying the necessary correction to the atomic scattering factors. The integrated intensities have been analysed and the temperature variation of the Debye-Waller factors of the metal (Cs+) ion and the pseudo ion (CB) have been estimated.

• Specific heat of YBa2Cu3O7−x from 4.2 to 60 K

The specific heat of superconducting oxide compound, YBa2Cu3O7 −x, is studied using a quasi-adiabatic calorimeter from 4.2 to 60 K. The analysis of the specific heat data below 15 K gives a value of 17 mJ/mole K2 for the electronic heat capacity coefficient. The value ofθD(0) is determined to be 397±8 K. The variation ofθD with temperature was calculated in the temperature range 4.2 to 60 K.

• Lattice dynamics of MgSiO3 perovskite

A lattice dynamical study of the geophysically important mineral MgSiO3 in its orthorhombic perovskite phase, with space group Pnma (D2h16) has been carried out using a rigid ion model, with the potential consisting of Coulombic and short-ranged interactions. With the help of program DISPR, the ionic charges and radii were optimized using the equilibrium conditions. The resulting potential model is employed to predict the elastic constants and the phonon dispersion relations. The computed long wavelength optic modes are in good agreement with the corresponding experimental Raman and infrared active bands. The phonon density of states has been obtained and is used to evaluate the specific heat, the mean square displacements and thermal parameters of atoms.

• Threshold pump strain for parametric amplification inn-indium antimonide

Phenomenological approach has been used to determine the threshold pump strain by assuming that at this strain the pump generates an electric field for which the drift velocity of the carriers equals the sound velocity. Numerical values obtained forn-InSb have been compared with similar studies which are based on Boltzmann transport approach.

• Mass enhancement factor for Pd and Pt

We report calculations of the mass enhancement factors for Pd and Pt by comparing the physical quantities using the interpolation scheme band structure, with the corresponding experimental data. Our results are compared with other theoretical calculations.

• # Pramana – Journal of Physics

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• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019