Structure of single-molecular-layer<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">MoS</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

An analysis of x-ray diffraction line shape and Raman-scattering results shows that single-molecular-layer ${\mathrm{MoS}}_{2}$, prepared by exfoliation of lithium-intercalated ${\mathrm{MoS}}_{2}$ powder in water, has a structure in which the Mo atoms are octahedrally coordinated, in contrast to the trigonal prismatic coordination of Mo in bulk ${\mathrm{MoS}}_{2}$. The octahedral coordination of single-layer ${\mathrm{MoS}}_{2}$ is strongly distorted, with a 2${\mathit{a}}_{0}$ superlattice. For a restacked film, the octahedral coordination of ${\mathrm{MoS}}_{2}$ appears to be a metastable structure. On heating or aging, it transforms back to the trigonal prismatic coordination.