Structure of nanocrystalline materials with intrinsic disorder from atomic pair distribution function analysis: The intercalation compound Ag_xMoS₂

The full three-dimensional structure of Ag-intercalated molybdenum disulfide has been experimentally determined. The atomic pair distribution function (PDF) analysis technique has been employed because of the very limited structural coherence in this nanocrystalline material. We found that at the atomic scale, this compound can be well-described as an assembly of anionic MoS₂ slabs encapsulating the Ag⁺ ions. Silver is found in an almost linear coordination of two sulfur atoms at 2.41 and 2.46 Å. The molybdenum atoms engage in strong metal-metal bonding giving rise to Mo-Mo zigzag chains within the MoS₂ slabs. This study demonstrates the effectiveness of PDF technique in determining the structure of poorly diffracting, heavily disordered, and nanocrystalline materials. The new structural information obtained for Ag_xMoS₂ could not have been obtained by any other currently available technique.