Joy Heising and Mercouri G. Kanatzidis
J. Am. Chem. Soc. 1999, 121, 638-643.
Department of Chemistry and Center for Fundamental Materials Research
Michigan State University, East Lansing, MI 48824
Abstract: There has been a lot of confusion about the nature of restacked
MoS2 and WS2. The structure has been proposed to
be trigonal TiS2 type with octahedral M4+ and called
1T-MoS2. The presence of a distortion in the metal plane which
gives rise to a superstructure has been suggested. We have performed electron
crystallographic studies on small (sub micron) single crystal domains of
restacked WS2 and MoS2 in order to solve their superstructure.
We find that what initially seems to be a trigonal crystal is actually
a "triplet" of three individual orthorhombic crystals. Using two-dimensional
hk0 data from films for both "triple" and "single" crystals we calculated
corresponding Patterson projections, which reveal a severe distortion in
the Mo/W plane, forming infinite zigzag chains. The projection of the structure
suggests M-M distances of 2.92 Å and 2.74 Å for MoS2
and WS2, respectively. Least squares refinement from the single
crystal data gives R1=13.3% for WS2 and R1=15.3%
for MoS2. Therefore, we submit that restacked MoS2
and WS2 are not 1T-form but rather WTe2 type.