Crystal Structure and Molecular Motion of Solid Carbon Disulfide

The crystal structure of CS₂ was determined at two temperatures from intensity data measured with a proportional counter and a modified Weissenberg apparatus. The orthorhombic cell [(a) 6.3437(8), (b) 5.5244(4), (c) 8.9971(7), 143°K, Cmca, $\text{Z\hspace{0.17em}=\hspace{0.17em}4}$ ] exhibited marked anisotropic thermal expansion, the coefficients of thermal expansion being ${\alpha }_a{\text{\hspace{0.17em}=\hspace{0.17em}630\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−6}}{\mathrm{°C}}^{\text{−1}}{\mathrm{,\; \alpha }}_b{\text{\hspace{0.17em}=\hspace{0.17em}570\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−6}}{\mathrm{°C}}^{\text{−1}}{\mathrm{,\; \alpha }}_c{\text{\hspace{0.17em}=\hspace{0.17em}−630\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−6}}{\mathrm{°C}}^{\text{−1}}.$ Positional and anisotropic thermal parameters were refined using upper‐angle data $(\sin \text{θ\hspace{0.17em}/\hspace{0.17em}λ\hspace{0.17em}≥\hspace{0.17em}0.35)}$ and the x‐ray results were compared with data from spectroscopic sources on the molecular motion of CS₂ in the solid. The unweighted reliability indices for the two refinements were 0.039 (148°K) and 0.056 (133°K). The carbon–sulfur bond length corrected for foreshortening due to libration was 1.560(3) Å (133°K) and 1.559 Å (148°K), in agreement with calculations of the length in the gas from spectral data (1.558 ± 0.0005) and electron diffraction (1.559 ± 0.002).