Effects of pressure on PbWO4-III

Abstract

In a hydrostatic pressure environment condition and in manual milling, respectively, investigations of PbWO 4 -III (P2 1 /n) have been performed by X-ray diffraction and Raman scattering techniques. Experiments found that PbWO 4 -III keeps its monoclinic structure under hydrostatic pressures with the sample's anisotropic compressibility up to 14.6 GPa, but transforms to PbWO 4 -I (I4 1 /a) in a grinding process. The stability and variability of PbWO 4 -III depending on the strain states were also explored by first-principles calculations of elasticity. Calculations show PbWO 4 -III has an anisotropic compressibility and a ductile nature with increasing pressure up to 15 GPa.

In-situ high-pressure Raman scattering studies in PbWO4 up to 48 GPa

“…11. In addition, there is also a nice correlation when the comparison is made with the thirty-one modes measured for PbWO 4 -III by Tan et al [33]. In this case, the wavenumbers shown in Table 2 at 8.9 GPa are obtained from the wavenumbers and the pressure coefficients reported at ambient pressure, assuming a linear dependence of the phonon frequencies with pressure (as we observed in phase III).…”

“…The fact that some of the calculated modes are nearly degenerated and that the Raman modes of the HP phase are broader than those of the low-pressure phase could explain why we observed only 48 of the 72 expected modes. We would like to note here, however, that we observed more Raman modes for the PbWO 4 -III than in previous studies [15,33]. The statement holds even when the comparison is made with ambient pressure studies [33] in which only thirty-one modes were measured.…”

“…We would like to note here, however, that we observed more Raman modes for the PbWO 4 -III than in previous studies [15,33]. The statement holds even when the comparison is made with ambient pressure studies [33] in which only thirty-one modes were measured. A comparison of the Raman modes here reported for PbWO 4 -III with previous experiments is also shown in Table 2.…”

“…Raman frequencies of PbWO 4 -III at different pressures compared with previous experiments[15,33] and calculations[15]. Pressure coefficients from the present work are also included.…”