D. Errandonea

Optical absorption of divalent metal tungstates: Correlation between the band-gap energy and the cation ionic radius

We have carried out optical-absorption and reflectance measurements at room temperature in single crystals of AWO4 tungstates (A = Ba, Ca, Cd, Cu, Pb, Sr, and Zn). From the experimental results their band-gap energy has been determined to be 5.26 eV (BaWO4), 5.08 eV (SrWO4), 4.94 eV (CaWO4), 4.15 eV (CdWO4), 3.9-4.4 eV (ZnWO4), 3.8-4.2 eV (PbWO4), and 2.3 eV (CuWO4). The results are discussed in terms of the electronic structure of the studied tungstates. It has been found that those compounds where only the s electron states of the A2+ cation hybridize with the O 2p and W 5d states (e.g BaWO4) have larger band-gap energies than those where also p, d, and f states of the A2+ cation contribute to the top of the valence band and the bottom of the conduction band (e.g. PbWO4). The results are of importance in view of the large discrepancies existent in prevoiusly published data.

High-pressure structural study of the scheelite tungstates CaWO4 and SrWO4

Angle-dispersive x-ray-diffraction and x-ray-absorption near-edge structure measurements have been performed on

The electronic structure of zircon-type orthovanadates: Effects of high-pressure and cation substitution

{\mathrm{CaWO}}_{4}

Melting of tantalum at high pressure determined by angle dispersive x-ray diffraction in a double-sided laser-heated diamond-anvil cell

and

The melting curve of ten metals up to 12 GPa and 1600 K

{\mathrm{SrWO}}_{4}

Determination of the high-pressure crystal structure of Ba W O 4 and Pb W O 4

up to pressures of approximately 20 GPa. Both materials display similar behavior in the range of pressures investigated in our experiments. As in the previously reported case of

High-pressure structural investigation of several zircon-type orthovanadates

{\mathrm{CaWO}}_{4}

Combined Raman scattering and ab initio investigation of pressure-induced structural phase transitions in the scintillator ZnWO 4

, under hydrostatic conditions

A combined high-pressure experimental and theoretical study of the electronic band-structure of scheelite-type AWO4 (A = Ca, Sr, Ba, Pb) compounds

{\mathrm{SrWO}}_{4}

Improving the understanding of the melting behaviour of Mo, Ta, and W at extreme pressures

undergoes a pressure-induced scheelite-to-fergusonite transition around 10 GPa. Our experimental results are compared to those found in the literature and are further supported by ab initio total-energy calculations, from which we also predict the instability at larger pressures of the fergusonite phases against an orthorhombic structure with space group Cmca. Finally, a linear relationship between the charge density in the