Computation of elastic constants and phonon frequencies in K-Cs melt.

Abstract

Using experimental compressibility the elastic constant ${\mathit{C}}_{11}$ of the alloy has been computed. ${\mathit{C}}_{11}$ has also been computed through Schofield's equations and the computations have been iterated with various values of the empty-core radius ${\mathit{r}}_{\mathit{c}}$. Care, however, has been taken to ascertain that the values of ${\mathit{r}}_{\mathit{c}}$ are near the free-ion value as given by Pauling. Thus a self-consistent method has been evolved in arriving at ${\mathit{C}}_{11}$. Further, the position of the effective-potential minima obtained through the empty-core model is found to be in good agreement with the maxima of the radial distribution function. The effective-potential functions at typical concentrations of Cs have been computed. The longitudinal and transverse phonon frequencies have been computed through the use of the Takeno-Goda equations. From the phonon frequencies the elastic constants have been computed. These values have been compared with those obtained from Schofield's ${\mathit{I}}_{1}$ and ${\mathit{I}}_{2}$ integrals. The elastic constants obtained by the two different methods are in fair agreement with each other. It is important to point out that the radial distribution functions are obtained from Fourier transformation of the total structure factors, which are found to be in very good agreement with experiment.