PIPPARD RELATIONS USING RAMAN DATA FOR $NH_{4}Cl$

Abstract

The Pippard relations have been modified spectroscopically for the first order, tricritical and the second order phase transitions for the $NH_{4}Cl$ crystal. Using our observed Raman frequencies for the $\nu_{5} (174 cm^{-1})$ lattice mode and $\nu_{2} (1708 cm^{-1})$ internal mode of $NH_{4}Cl$, we have obtained a linear relationship betweenthe specific heat $C_{p}$ and the frequency shifts $(\partial 1 nv / \partial T)_{P}$ in the vicinity of the $\lambda$ phase transitions in this crystal. Our data give reasonable values for the $(dP/dT)_{1}$ near the first order, tricritical and the second order phase transitions in $NH_{4}C1$.