Li2Ni2Mo3Ol2 is orthorhombic, a = 10.423 (3), b --17.525 (4), c = 5-074 (1) A, space group Pmcn with Z = 4. 2717 independent reflexions were collected and the structure was refined to an R value of 0.053. The average Mo-O and (Ni,Li)-O distances are 1.774 and 2.097 A, respectively. The close-packed sheets of O are composed of three-square-wide bands of Wells's No. 9 regular net, held together by semi-regular single chains of triangles. There are two identical sheets in the stacking sequence, and the regular and semi-regular voids between the O atoms are filled by the cations: Ni and Li occupy, in various proportions, the trigonal prism (M1), the distorted (M2) and the regular (M3) trigonal antiprisms, and Mo occupies the elongated tetrahedral voids.
ExperimentalSingle crystals of Li2Ni2Mo3Oi2 were produced accidentally during an attempt to grow nickel-olivine crystals by a flux method (Ozima & Zoltai, 1976). One of these crystals, 0.07 × 0.07 x 0-08 mm, was mounted on an automated, four-circle Rigaku diffractometer and three-dimensional intensities were collected with Mo Ka radiation, monochromated by a graphite plate.The intensities of the reflexions were collected in the o9-20 mode. The intensities of three standard reflexions were checked after every 50 measurements. 2980 independent intensities were collected up to 20 = 80 °. Of these, 2717 intensities were sufficiently strong for consideration. All intensities were corrected for Lorentz and polarization effects, but no corrections were made for primary and secondary extinction, or for absorption. The last appeared to be unnecessary as the crystal was almost an equidimensional cube.
Structure determination and refinementThree-dimensional Patterson maps were computed and were solved for the Mo and Ni atomic coordinates by recognition of the vectors of these relatively heavy atoms. The locations of the O and Li atoms were obtained from a Fourier difference synthesis. The structure was subsequently refined by minimizing E (IFol --IFcl) 2 through full-matrix least-squares calculations based on the 2717 observed intensities. Anisotropic thermal parameters for Mo, Ni and O and isotropic thermal parameters for Li were also calculated. The final R value obtained was 0.053. The atomic coordinates are given in Table 1. The Ni-Li distribution pattern in M1, M2 and M3 sites was also determined. The M1 site is occupied by Li and the M2 and M3 sites by Ni and Li in the ratio Ni : Li 0-731:0.269 and 0.538:0.462 respectively.
Auszug Die Struktur wurde nach der Methode der kleinsten Quadrate bis zu dem Endwert R = 7,60/0 verfeinert. Die Intensitatcn I(hkl) wurden an dem gleichen synthetischen Material gemessen, das schon der ersten Strukturbestimmung1 diente. Gegentiber den frtiheren Daten ergaben sich leichte Abweichungen bei den Atomparametern und etwas bedeutendere Diffcrenzen bei den GraBen der Warmeschwingungen.
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