Jacob Philip
Articles written in Pramana – Journal of Physics
Volume 8 Issue 4 April 1977 pp 348-362 Solids
Cuspidal edges for elastic wave surfaces for cubic crystals
The paper deals with a detailed numerical study of the sections of the inverse and ray velocity surfaces for cubic crystals. The figures for the sections of the inverse and ray surfaces by the (001) and (110) planes have been plotted for over 65 crystals and from these, the nature of the cuspidal edges has been discussed. Typical graphs of the inverse and ray surfaces have been given. The parameters characterising the dimensions of the cusps have been tabulated. It is shown that the A-15 compounds exhibit very unusual and interesting wave surfaces at temperatures below superconducting critical temperatures.
Volume 10 Issue 3 March 1978 pp 311-317 Solids
Interlattice displacements and elastic constants of the A-15 compounds V_{3}Si, V_{3}Ge and Nb_{3}Sn
General expressions for the interlattice displacements of the A-15 structure compounds are obtained in terms of the strain components making use of the deformation theory. The nature of the interlattice displacements of all the 8 atoms in the unit cell is discussed. It is found that the interlattice displacements occur in such a way that the pair of atoms along any linear chain move in opposite directions with equal magnitudes. Expression for the strain energy of these compounds is developed using deformation theory and this is compared with the strain energy expression from continuum theory to obtain the elastic constants. The theoretical values of the elastic constants fairly agree with the experimental values for V_{3} Si, V_{3}Ge and Nb_{3} Sn.
Volume 12 Issue 6 June 1979 pp 679-697 Crystallography
Neutron scattering by anharmonic crystals and the effect of sublattice displacements
A theory has been given for the scattering of neutrons by anharmonic crystals, for which terms of the type
Volume 29 Issue 4 October 1987 pp 391-398 Condensed Matter Physics
Elastic nonlinearity parameters of tetragonal crystals
The equations of motion for the propagation of finite amplitude elastic waves in crystals of tetragonal symmetry have been derived starting from the expression for the elastic strain energy. The equations have been solved for a finite amplitude sinusoidal wave propagating along the pure mode directions which are [100], [110] and [001] for the tetragonal group TI. The solutions corresponding to longitudinal wave propagation yield expressions for the amplitudes of the fundamental and generated second harmonic for these directions in terms of certain combinations of second and third order elastic constants of the medium. The results will aid the experimenter to determine these constants using ultrasonic harmonic generation technique.
Volume 32 Issue 6 June 1989 pp 821-830 Condensed Matter Physics
Thermal diffusion near glass transition in Ge-Se glasses measured by photoacoustics
K N Madhusoodanan Jacob Philip
The glass transition in Ge_{x}Se_{1−x}) (0·1 ⩽
Volume 33 Issue 6 December 1989 pp 705-712 Condensed Matter Physics
Composition dependence of the energy gap and thermal diffusivity in bulk As-Se glasses
K N Madhusoodanan Jacob Philip
We have measured the composition dependence of the optical energy gap and thermal diffusivity in bulk As_{x}Se_{1−x} (0.10⩽
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