Articles written in Pramana – Journal of Physics
Volume 20 Issue 6 June 1983 pp 491-501 Solid State Physics
The second order pseudopotential theory suggests the possibility of a break-up of the total energy of simple metals into a purely volume-dependent part and an effective central pairwise interaction between ions. In the present paper finite contributions for these two parts of the energy have been extracted in a form convenient for calculation. Using the local Heine-Abarenkov model potential, a reliable effective ion-ion interaction is generated and the volume-dependent energy is calculated for Al. The relative contributions of the effective interaction and the volume-dependent energy term to various metallic properties are also calculated. The importance of volume dependence on the effective interaction is also discussed.
The interactomic force constants upto eighth neighbour are derived from the effective interaction and it is found that the force constants beyond the third neighbour are negligibly small. This result is also confirmed by the calculation of dispersion curves with force constants obtained from the effective interaction upto the third neighbour which is found to reproduce the results of the full pseudopotential calculations. The force constants obtained are also used to study some finite temperature properties of Al in the quasi-harmonic approximation and the limitations of the theory are pointed out.
Volume 26 Issue 3 March 1986 pp 231-237 Solid State Physics
A Unified study of lattice-mechanical properties of lead using energy-dependent pseudopotential is carried out. Energy dependence in pseudopotential is considered through the effective mass approximation; the pseudopotential model chosen is the local Heine-Abarenkov model potential. Properties studied include cohesive energy, equilibrium lattice parameter, second-order elastic constants, pressure derivative of second-order elastic constants, equation of state (at
Volume 28 Issue 6 June 1987 pp 689-697 Condensed Matter Physics
A comprehensive unified study of fcc alkaline earth metal Ca, Sr and the bcc phase of Sr and Ba has been made. Properties studied include equilibrium lattice parameter, total crystal energy, second order elastic constants, pressure derivative of the second order elastic constants and phonon spectrum in the symmetry direction. The results obtained show an overall agreement with experiment. The results partially reproduced the experimentally observed phonon-crossover in Ba, and this has been found as the many-body effect in lattice dynamics.
Volume 59 Issue 5 November 2002 pp 849-858
P N Prakash T S Datta B P Ajith Kumar J Antony P Barua J Chacko A Choudhury G K Chadhari S Ghosh S Kar S A Krishnan Manoj Kumar Rajesh Kumar A Mandal D S Mathuria R S Meena R Mehta K K Mistri A Pandey M V Suresh Babu B K Sahu A Sarkar S S K Sonti A Rai S Venkatramanan J Zacharias R K Bhowmik A Roy
This paper reports the construction of a superconducting linear accelerator as a booster to the 15 UD Pelletron accelerator at Nuclear Science Centre, New Delhi. The LINAC will use superconducting niobium quarter wave resonators as the accelerating element. Construction of the linear accelerator has progressed sufficiently. Details of the entire accelerator system including the cryogenics facility, RF electronics development, facilities for fabricating niobium resonators indigenously, and present status of the project are presented.
Volume 59 Issue 5 November 2002 pp 881-884
An on-line test of the LINAC superbuncher at Nuclear Science Centre has been successfully performed. DC O7+ beam of nominal energy 92 MeV was accelerated through the superbuncher resonator, operating at a field of 4.54 MV/m. The total energy gain of the beam was measured to be 4.5 MeV. For the pulsed beam test a phase locked bunched beam of O7+ of nominal energy 92 MeV, FWHM 1.3 ns from the pre-tandem multiharmonic buncher was injected into the superbuncher. By properly adjusting the phase and amplitude of the resonator, the best FWHM of the bunched beam was measured to be 185 ps near the entrance of the first LINAC module. Fully depleted cooled surface barrier detector was used for measuring the time width. In a separate experiment the intrinsic time resolution of the same detector was measured to be 134 ps. Consequently the intrinsic time width of the bunched beam, after correcting for the detector resolution, would be 127 ps. Details of the experiment and results are presented.