Neutron powder-profile study of chlorofluoromethane.
The crystal structure of chlorofluoromethane, CH(2)ClF, has been determined at 100 and 30 K using indexing, packing considerations and Rietveld refinement of neutron powder profiles. There is only one phase, in monoclinic space group P2(1) and with two molecules in the unit cell occupying general positions. The structure has close packing in several directions and there are weak hydrogen bonds forming zigzag chains.
Raman and infrared spectra of solid chlorofluoromethane
Raman and infrared spectra of solid CH 2 ClF (Freon 31) were recorded in both the lattice and internal mode regions for samples at temperatures between 12 and 125 K. No evidence of any solid-state phase transition was found, but some thin-film samples deposited at low temperatures appear to exist in a metastable phase. Spectra of the stable phase are compatible with a non-centrosymmetric unit cell containing four molecules. Lattice peaks are assigned on the basis of geometrical and intensity arguments
Crystal structures of methylene bromide and methylene iodide
The crystal structures of the three solid phases of methylene iodide and the stable phase of deuterated methylene bromide have been determined using the neutron powder profile structure refinement technique. For CH2I2, both phase I at 50K and phase III at 16K, and for CD2Br2, the stable phase at 15K, have eight molecules per unit cell on general sites of the monoclinic space group C2/c. The structure of CH2I2, phase II, has been determined at 16K, 30K, 50K and 255K. This phase is face centred orthorhombic, space group Fmm2, with four molecules per unit cell on sites with C 2v symmetry. Molecular bond lengths and angles are given for all structures. The lattice energy of each structure has been calculated using an empirical potential. Phase II is found to be the most stable phase for CH2I2, but the energy differences between all three phases are small.