Calculation of the Raman frequencies of lattice modes in the disordered phase II of NH4Br at high pressures

摘要

The Raman frequencies are calculated here at various temperatures for the v7(56 cm-1) and v_5 (134 cm~(-1)) lattice modes in the disordered phase II of NH4Br. The lattice parameter data obtained at zero pressure are used to calculate the Raman frequencies of those modes studied for constant pressures of 0.1, 108, and 637.5 MPa in phase II of the NH4Br crystal. Through the mode Gruneisen parameter which is kept constant in the disordered phase II, the Raman frequencies calculated decrease linearly with increasing temperature at all fixed pressures for both lattice modes of NH_4Br. Measurements of the Raman frequencies for the lattice modes of interest can be conducted to examine our calculations under the temperature and pressure variations given here for NH_4Br.2010 Physics Essays Publication.