A physical understanding of the nature of the force constants and kinetic constants in molecules leads to a stringent application of the provisions of the group theoretical techniques introduced by Wilson in the study of molecular vibrations. This procedure is applied here to the evaluation of force constants and the mean amplitudes of eighteen tetrahedral XY₄ molecules with highly satisfactory results.

Using Wilson’s F-G matrix method a normal co-ordinate analysis of the spectral frequencies and form of the zero-wave vector vibrations of the high temperature superconductor, orthorhombic DyBa₂Cu₃O₇ has been performed. The vibrational frequencies and the potential energy distribution of the 21 infrared-active and 15 Raman-active modes are presented. The potential constants employed here are presented and evaluated vibrational frequencies are compared with the available experimental values.

The critical current densities (J_c) have been measured at 77K in high pressure oxygen sputtered thin films of YBa₂Cu₃O_7−x superconductor using the non-resonant rf absorption technique. High values ofJ_c (∼ 10⁵ A/cm²) are observed in these relatively large area (∼ 1·2 cm²) films.