Calculation of the Raman frequency and the damping constant of a coupled mode in the ferroelectric and paraelectric phases in KH2PO4

Abstract

AbstractThe Raman frequency of the coupled mode $\omega _ - $ associated with the order parameter is calculated as a function of pressure from the mean field theory in the ferroelecric phase of KDP. Using the frequencies of the coupled mode, the pressure dependence of the damping constant $\Gamma _ - $ is calculated by the proton spin lattice relaxation time and by the energy fluctuation of this mode of KDP in the ferroelectric (FE) phase. For the paraelectric (PE) phase, the Raman frequency of the coupled mode $\omega _ - $ is calculated as a function of temperature at 6.54 kbar. The temperature dependence of the damping constant $\Gamma _ - $ is performed only by the energy fluctuation of the coupled mode $\omega _ - $ in the PE phase of KDP. The values of the activation energy U are extracted from the pressure and temperature dependence of the damping constant $\Gamma _ - $ of this coupled mode $\omega _ - $ for both FE and PE phases of KDP.