Electronic structures of silicates other than olivines and SiO

Electronic structures of silicates other than olivines and SiO,  

The electronic structures of silicate minerals of polymerization intermediate between nesosilicates and tektosilicates have been studied to a lesser extent than have SiOj or the olivines. The complexity of their crystal structures makes calculation difficult, and their diversity in terms of local chemical environment makes phenomenological assignment of their spectra difficult. Nonetheless, some recent comparative studies have given valuable electronic structure information on such materials. 

Glasses along the (Na20)/Si02)i i series have also been studied by Si NMR (Stebbins, 1987 Selvaray et al., 1985). Stebbins (1987) demonstrated, for sodium silicate glasses, the existence of polymerized species not dictated by the stoichiometry (e.g., in NajSijO composition glass), which in crystalline form contains entirely species. He found 

For silicates such as MgSiO, differences in electronic structure with respect to SiOj are more elusive. Si spectra (Dodd and Glenn, 1969  

It is surprising that no significant differences in Si Ap x-ray emission spectra are observed between olivines and pyrosilicates, since the P Ap spectra of pyrophosphates (Mazalov et al., 1979) clearly show extra features around the P 3s-0 2p cr position arising from symmetry lowering. 

---