Lattice Parameters Between 5° and 298°K and Crystal Structure at 5°K of Cobalt Chloride Dihydrate

Lattice dimensions for CoCl2·2H2O as a function of temperature have been determined in the range between 4° and 298°K. A very small anomaly has been found in the b0 lattice parameter near the Neél temperature. The crystal structure at 5°K has been refined using single-crystal diffractometer Mo Kα x-ray intensity data from hk0 and h0l zones. The unit-cell dimensions contract anisotropically from values of a0=7.279, b0=8.553, c0=3.569, β=97.58° at 298°K to values of a0=7.206, b0=8.498, c0=3.564 Å, β=97.60° at 5°K. However, the fractional atomic coordinates of the 5°K structure differ only by a maximum of four standard deviations from those previously determined at room temperature.