Temperature dependence of the structures of solution-grown and melt-grown samples of n-hexatetracontane

The crystal structures of solution-grown and melt-grown polycrystalline samples of n-hexatetracontane (n-C46H94) in the temperature range 293-359 K have been investigated by X-ray powder diffraction. The solution-grown sample has an orthorhombic structure, with space group Pbc2(1) and cell dimensions a = 4.952 Angstrom, b = 7.424 Angstrom, and c = 120.95 Angstrom. While heating this sample a gradual transition to a monoclinic phase takes place, with onset temperature 335 K. At temperatures close to the melting point two configurations of the ab plane have been observed. Cooling a sample from the melt results in a mixture of a monoclinic and an orthorhombic structure. Rietveld refinements of the structures of solution-grown and melt-grown samples at 293 K have been performed. (C) 1997 International Centre for Diffraction Data.