THE CRYSTAL-STRUCTURE OF 4-METHYL PYRIDINE AT 4.5-K

The crystal and molecular structure of deuterated 4-methyl pyridine C6D7N has been determined at 4.5 K using pulsed neutron powder diffraction. It crystallises in the space group I4(1)/a with a = 7.5338(1) angstrom, c = 18.4960(1) angstrom and Z = 8. The structure is the same as that determined by Ohms et al. [J. Chem. Phys. 83 (1985) 273 - 279] for the hydrogenous material at 120 K, and there appears to be no phase transition down to 4.5 K. Our results contradict the conclusions of Biswas [Indian J. Physics 35 (1961) 261 - 268], who assumed a monoclinic space group P2(1)/c in interpreting X-ray powder diffraction data at 93 K.