The iron nitridometalates Li2[(Li(1-x)Fe(I)(x))N] display ferromagnetic ordering and spin freezing. Large magnetic moments up to 5.0mu(B)/Fe are found in the magnetization. In Mössbauer effect studies huge hyperfine magnetic fields up to 696 kOe are observed at specific Fe sites. These extraordinary fields and moments originate in an unusual ligand field splitting for those Fe species leading [within local spin density approximation (LSDA)] to a localized orbitally degenerate doublet. Including spin-orbit interaction and strong intra-atomic electron correlation (LDA+SO+U) gives rise to a large orbital momentum.

Abstract. Metavariscite, A1PO4.2H20, monoclinic, e21/n, a=5.178 (2), b=9-514 (2), c=8.454 (2) .&, fl= 90.35 (2) °, Z=4, Dm=2"54, Dx=2"535 gcm -3. Material from Utalith Hill, Lucin, Utah, U.S.A.t PO4 tetrahedra share vertices with four AIO4(OH2)2 octahedra and vice versa. With AI-..O distances of 1.892 (2) and 1.953 (2) A the two waters coordinate the aluminum in cis-position and donate two single and quite short and two bifurcated longer hydrogen bonds, respectively, to phosphate oxygens. None of the hydrogen bonds is along an octahedron edge.Least-squares refinement on F was started from nonhydrogen atom parameters reported by Borensztajn (1966). The four hydrogen atoms could easily be located as the highest peaks in a difference map. The final R was 0.027 for all reflexions (0-023 for significant reflexions only).The form factors used were those of Hanson, Herman, Lea & Skillman (1964) for P, AI and O, and of Stewart, Davidson & Simpson (1965) for H. The observations were weighted according to w= 1/a~-with av evaluated from the measurements.Introduction. Cell constants were determined from diffractometric measurements. The systematic absences are hOl for h + l odd and 0k0 for k odd. The intensities of 1215 independent reflexions with 0 < 30 ° were measured with Zr-filtered Mo K~ radiation on a tape-controlled Siemens automatic diffractometer with 0/20 scan.The crystal size was approximately 0.3 ×0.3 x0.2 ram. 1067 reflexions had significant intensities. No correction for absorption (/z=8-2 cm -1) was applied.

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Pale yellow transparent single crystals of Ca6[Al2Nö] (P 2\/c, No. 14, a = 693.7(3), b = 614.9(3), c = 987.1(5) pm, ß = 94.01(5)°; Z = 4) and colourless transparent single crystals of Ba.^ALN*] (Pnna, No. 52, a = 617.9(2), b = 1005.2(4), c = 1023.0(4) pm; Z = 4) were obtained from reactions of mixtures of the representative metals with nitrogen at Tmax = 1000 °C. The crystal structure of CaöfALNft] contains isolated units [ALNftJ12-built of two edge-sharing tetrahedra. Ba3[ALN4] is an isotype of S r^A bN^. The crystal structure contains infinite chains ^ [A1N^T2] of trans edge-sharing tetrahedra.