Effect of high pressure on the Raman and Electronic Absorption Spectra of PbMoO4 and PbWO4.

The effect of pressure on the Raman spectrum of Scheelite Structure Compounds PbMoO4 and PbWO4 has been investigated, using a diamond anvil cell. The electronic absorption edge in PbMoO4 was also studied up to 100 kbar. Both in PbMoO4 and PbWO4 new Raman peaks appear at 90 kbar and 45 kbar respectively due to first-order phase transition. The electronic absorption edge in PbMoO4 decreases in energy at he rate of 5 meV/kbar. These results are discussed in terms of the crystal chemistry and electronic structure of ABO4 oxide compounds.