Knowledge Bank

The Pippard relations have been modified spectroscopically for the first order, tricritical and the second order phase transitions for the $NH4Cl$ crystal. Using our observed Raman frequencies for the $\nu 5(174cm-1)$ lattice mode and $\nu 2(1708cm-1)$ internal mode of $NH4Cl$, we have obtained a linear relationship betweenthe specific heat $Cp$ and the frequency shifts $(\partial 1nv/\partial T)P$ 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 $NH4C1$.