Cation distribution in (Mg,Zn)₂SiO₄ olivine solid solution: a ²⁹Si MAS NMR and first-principles calculation study

Abstract

We have applied ²⁹Si MAS NMR together with first-principles calculation to gain new insights into the cation (Mg, Zn) distribution in (Mg,Zn)₂SiO₄ olivine solid solution, as well as the correlation between ²⁹Si chemical shift and local structures associated with cation distributions. It was demonstrated that ²⁹Si MAS NMR is capable of probing/quantifying the occupancy of cations in the M1 and M2 octahedral sites, and Zn has a preference for M1 sites. This study also revealed that cation substitutions in neighboring edge-shared octahedral sites have greater influence on the ²⁹Si chemical shift as compared to corner-shared sites for olivine.