Lattice Dynamics and Temperature Dependence of the First-Order Raman Spectra for PbMoO ₄ Crystal

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The phonon dispersion carves for PbMoO₄ crystal were calculated on the basis of a rigid-ion model. The first-order Raman spectra of A_g mode PbMoO₄ crystal were measured in a temperature range from 77 to 473 K. The temperature dependence of the linewidths was analyzed by using the phonon dispersion curves, and the results showed that it was caused approximately by the cubic anharmonic term in crystal potential energy. The temperature dependence of the frequency shift of the A_g mode was analyzed by using the lattice dynamical perturbative treatment. We found that the quartic anharminic term of the first-order perturbation, as well as the cubic term of the second-order one contributes to the temperature dependence of the frequency shift of the A_g mode in the PbMoO₄ crystal.