Polarized two-phonon Raman and two-phonon infrared spectra of amorphous ${\mathrm{As}}_2$${\mathrm{S}}_3$ have been measured at 300 and 80 K and compared to analogous spectra of crystalline ${\mathrm{As}}_2$${\mathrm{S}}_3$. The comparison of the two-phonon spectra of the crystalline and amorphous forms leads to a better understanding of those vibrational modes which determine the subtleties of the Raman and infrared spectra in the glassy phase. In particular, this comparison suggests that, when the effects of local fields are included, some selection rules imposed by the crystalline layers may also be applicable to the glassy phase. However, great caution must be exercised in any attempt to draw structural inferences from these vibrational data.

• Received 21 July 1977

DOI:https://doi.org/10.1103/PhysRevB.16.4511