Collective excitations in liquid cesium using a theory of phonons in amorphous solids

A theory of phonons in amorphous solids as developed by Takeno and Goda using a self-consistent method, is applied for the numerical calculations of the collective excitations in the longitudinal and the transverse modes in liquid cesium at its melting temperature. The pair potential used for these calculations is the model potential obtained from Ashcroft's pseudopotential with Singwi's dielectric screening procedure for liquid cesium. An independent estimation of these collective excitations is done using the Hubbard and Beeby approach. Besides, an effort is also made to calculate the phonon lifetimes in the large wave vector transfer region where the collective excitations are observable. Results of the phonon dispersion obtained from these two methods are compared and good agreement is observed. (author)