ATOMIC DISPLACEMENT PARAMETERS FOR NI(ND3)(4)(NO2)(2) FROM 9 K X-RAY AND 13 K TIME-OF-FLIGHT NEUTRON-DIFFRACTION DATA

Structural parameters derived from 9(1)K X-ray diffraction data and 13 (1)K time-of-flight neutron diffraction data on perdeuterated tetraamm inedinitro-nickel(II), Ni(ND3)(4)(NO2)(2), are compared. It is shown t hat excellent agreement can be obtained for both positional and therma l parameters derived separately from the two experiments, provided tha t great care is taken in all steps of the process, including data coll ection, data reduction, and nuclear and electronic structure refinemen t. The mean difference in the thermal parameters, <\Delta U-ij\>, is a s low as 0.00034 Angstrom(2) and <(Delta U-ij/sigma)(2) >(1/2) = 1.92, showing that, even without any form of scaling between the parameters , the same values can be obtained. This, compared with other such stud ies, indicates that time-of-flight neutron diffraction data can give s tructural information of a quality comparable to monochromatic neutron diffraction. The excellent correspondence between the thermal paramet ers derived separately from X-ray and neutron diffraction data gives c onfidence in the deconvolution of the thermal motion from the X-ray di ffraction data, which is necessary for any study of a static electron density distribution.