Knowledge Bank

The molar volume is calculated as a function of pressure using the observed Raman frequencies of the $\nu 7$ TA (57 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$) and $\nu 5$ TO (140 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$) modes of NH$4$Br in the disordered phase II. This calculation is performed through the mode Gruneisen parameter which is taken as a constant for each mode studied throughout the phase II of this crystal. Measurements of the lattice parameter (molar volume) can be performed to examine our calculations from the Raman frequencies studied here for NH$4$Br.