Knowledge Bank

We are carrying out calculations on several forms of sulfur, including $S6,S12$ and rhombic $S8$. We began with the atom-atom potential reported by Rinaldi and $Pawley1$ for rhombic $S8$; however, this gave Raman lattice modes much smaller than observed in $S6$. Upon calculating lattice modes for rhombic $S8$, we find values substantially smaller than reported by Rinaldi and Pawley; this is no doubt due to their use of a rather small cut-off distance. 50{\AA}. We are using the same type of potential, but with adjustment of the three parameters toward an optimum fit for the structures, energies nd lattice vibrations of all three forms. Our program can also calculate the internal modes in the crystal with only a modest increase in computer time, over that for external modes only. Some of the internal modes are markedly increased as a result of the crystal interactions, Current results of the work will be reported.