COMPUTATION OF COLLECTIVE EXCITATIONS AND ELASTIC-CONSTANTS OF EXPANDED TRIGONAL TELLURIUM

The potential function derived from experimental structure factor data gives a repulsive minimum and also an attractive minimum. These two m inima correspond to the first and second nearest-neighbour distances. Similar results have been obtained through the use of Percus-Yevick (P Y) and hyper-netted chain (HNC) equations. The Hafner molecular dynami cs results also show a similar trend. The first, second and third deri vatives of the potential function have been obtained from the expressi on of the potential function. The first and second derivatives have be en used to compute the phonon frequencies using Bhatia and Singh's (BS ) method. The phonon frequencies obtained from Hubbard and Beeby's (HB ) method show similar results. The elastic constants have also been ca lculated and the values obtained for C-11 by different methods are in good agreement. The Gruneisen constant has been calculated by two diff erent methods which are in very good agreement with each other. From t he Gruneisen constant the pressure derivative of the diffusion coeffic ient has been obtained and has been compared with that of Swalin's equ ation. The results are in excellent agreement with each other.