A high pressure Raman study of the vibrational modes in AlPO sub 4 and SiO sub 2 (alpha-QUARTZ).
01 January 1987
The pressure dependence of the optical phonon frequencies in berlinite (AlPO sub 4) and alpha-quartz has been investigated by high pressure Raman scattering experiments, using a diamond cell; berlinite was studied up to 12 GPa and alpha-quartz to 20 GPa. The A sub 1 soft phonon mode at 216 cm sup -1 in AlPO sub 4 and the corresponding mode in alpha-quartz at 206 cm sup -1 exhibit similar but anomalously large and nonlinear pressure dependencies. Further, these two modes exhibit striking decreases in their widths with increasing pressure. These changes appear to be connected with the decoupling of the strong anharmonic interactions of the A sub 1 soft mode phonon with the two-phonon (acoustic) states in alpha-quartz and with one-phonon (optical) and two-phonon (acoustic) states in AlPO sub 4.