The wulfenite—stolzite series: centric or acentric structures?
2008; Cambridge University Press; Volume: 72; Issue: 4 Linguagem: Inglês
10.1180/minmag.2008.072.4.987
ISSN1471-8022
AutoresL. Secco, Fabrizio Nestola, A. Dal Negro,
Tópico(s)Polyoxometalates: Synthesis and Applications
ResumoAbstract Three natural crystals of the wulfenite (PbMoO 4 )—stolzite (PbWO 4 ) series were investigated by single-crystal X-ray diffraction. The results indicate that the symmetry is I4 1 /a from nearly pure wulfenite to intermediate compositions, in contrast to previous work which claimed a symmetry change to 74 symmetry (acentric) for intermediate compositions compared with I4 1 /a (centric space group) for the end-members. The results reported here show that the reflections violating I4 1 /a symmetry observed in this work and in a previous study are related primarily to λ/2 effects, even if Renninger effects are not excluded. Consequently, we find that the I4 1 /a symmetry is retained throughout the wulfenite— stolzite.
Referência(s)