Knowledge Bank

Raman frequency shifts for the $(144cm-1)$ TO mode of $NH4C1$ have been calculated at various temperatures for zero pressure near phase transitions $(P=O,T=241.5K)$ in this crystal system.By defining the mode Gr""{u}neisen parameter at cons""{a}nt pressure as , we have obtained $\nu =2.1293$ for the 144 cm Raman mode across phase traHsition region using our observed Raman frequency data for this mode and the length-change data of $NH4Cl$ from the literature. Using this constant * value, we have calculated the Raman frequencies for the $\nu 5(144cm-1)$ TO mode.Comparson between our calculated and observed values for this Raman mode in $NH4CI$ gives good agreement.