Microwave-assisted intercalation: exploring electronic and structural features of metastable MMo6S8 (M = Ag, Sn)

Abstract

Presented in this work is a synthetic approach for metastable Type I Chevrel phase sulfides, MMo₆S₈ (M = Ag, Sn), utilizing rapid microwave-assisted medium temperature intercalation. Using X-ray absorption spectroscopy the electronic structure and local coordination of sulfur and molybdenum bonding environments are probed as a function of a Type I metal intercalant. Intercalant promoter-induced electron donation effects were observed through analysis of the sulfur K-edge pre-edge feature and Mo L₃-edge in the X-ray absorption near edge regions. Calculated electron density maps reveal more covalent interactions between Ag and S atoms versus more ionic interactions between Sn and S. Changes in the Chevrel phase structure upon intercalation are investigated through Mo K-edge extended X-ray absorption fine structure analysis. Evaluation of Mo–Mo intracluster distances allows the cluster anisotropy of Type I CPs to be calculated as low as 1.84%. These findings help elucidate how electronic and local structures can be modulated through intercalation and the importance of cation identity to fine tune structures.