Local and intermediate-range structure of amorphous MoS3: Model calculation study

The amorphous phase of Mo${\mathrm{S}}_3$, which has no crystalline counterpart, is prepared through the thermal decomposition of ammonium thiomolybdate. The structure of this amorphous phase has been analyzed through a combination of x-ray diffraction and computer calculation of model structures. Both the x-ray diffraction pattern and its Fourier transform, the pair distribution function, were modeled. In $r$ space there were four prominent distances whose positions and relative contributions required fitting while in $k$ space there was a prominent well-defined peak at ∼ 1 ${\mathrm{\AA }}^{-1\mathrm{}}$ together with diffuse oscillations out to ∼ 15-16 ${\mathrm{\AA }}^{-1\mathrm{}}$. Relevant spectroscopic and chemical data were used to rationalize a consistent structure. A basic chainlike arrangement of dimerized Mo atoms separated by triangularly coordinated S atoms with disulfur bonds, provided the starting point. The final structure consisted of pairs of (coupled) chains with significant deviations or bendings from parallel alignment. These paired flat chains could then be stacked as they would naturally be in the material to produce the requisite planar correlations for the 1-${\mathrm{\AA }}^{-1\mathrm{}}$ peak in $k$ space. The final overall fit in both $k$ and $r$ space was considered good.