CALCULATION OF THE RAMAN FREQUENCIES AS A FUNCTION OF TEMPERATURE IN PHASE III OF NH4I

Abstract

We study here the temperature dependence of the Raman frequencies for the overtone 2ν6 of the librational mode ν6 in phase III of NH 4 I . By using the experimental infrared frequencies of the 2ν6 mode, we predict the Raman frequencies of this overtone 2ν6 mode as a function of temperature at atmospheric pressure in phase III of NH 4 I . Our calculations indicate that the Raman frequencies of 2ν6 exhibit anomalous behavior at around 110 K (P = 0) in phase III of NH 4 I , as observed experimentally.