Compounds A2 Research Articles

Nonstoichiometric oxides with a layer structure: The compounds A1− x(Ti 1− xM 1+ x)O 5

New nonstoichiometric oxides A 1− x (Ti 1− x Nb 1+ x )O 5 and tantalates ATiTaO 5 with a layer structure of the KTiNbO 5 type have been isolated, with A = K, Rb, Tl, Cs. These oxides, which are orthorhombic, space group Pnma, are characterized by a preferential occupation of one type of site 4 c by the titanium atoms. The structural evolution as a function of composition and the stability of these compounds are discussed.

Intergrowth structure of Eu1–pCr2Se4–p(p= 0·29) and isotypic compounds. A novel type of crystal structure with three incommensurate periodicities in one direction: X-ray study

The structure of the compounds A1–pCr2X4–p(A = Pb, Eu, Sr, or Ba; X = S or Se), as determined by X-ray diffraction, consists of three structural units which have a common hexagonal basal plane, but different, mutually incommensurate c-axes.

A series of new compounds A3+Fe 2 O 4 ( A = Ho, Er, Tm, Yb, and Lu)

A series of new compounds A Fe 2 O 4 ( A = Ho, Er, Tm, Yb, and Lu) have been successfully synthesized under the lower oxygen partial pressures at 1200°C and their unit cell dimensions were determined.

Structure of hexaammines of aluminum borohydride and chloroborohydrides

1. It was shown by the method of IR spectroscopy that under the action of ammonia on aluminum borohydride, monochloroborohydride, and dichloroborohydride, there is a nonsymmetrical cleavage of the A1H2B groups with the formation of “salt-like” compounds, constructed from [A1(CH3)6]3+, Cl−, and BH 4 − . 2. The parameters of the rhombic cells of the compounds A1(BH4)3·6NH3, A1(BH4)2C1·6NH3, A1(BH4)C12·6NH3, and A1C13·6NH3. 3. The valence force constant of the Al-N bond was calculated in the approximation of a “diatomic” model, and the Al-N interatomic distance was determined in the octahedron [A1(NH3)6]3+.

Spektroskopische Untersuchungen zum Jahn-Teller-Effekt des Cu2+-Ions in Verbindungen vom Typ A2 CuL6, I / Spectroscopic Ivestigations with Respect to the Jahn-Teller-Effect of Cu(II) in Compounds of the Type A2CuL6, I

Structural relations between perovskite-related lattices of the type A2CuL6 and the perovskite compounds A2 (12) [BCu](6)L6 (1: 1 order in the octahedral sites, elpasolite type) are demonstrated by two examples, the compounds A,Cu(OH)6 [A = Ba, Sr] and Ba2CuF6. From the ESR spectra a coupling of Jahn-Teller-distorted Cu-ligand-octahedra in these compounds corresponding to a “disturbed” type of antiferrodistortive order can be deduced. This result is in agreement with recent X-ray structure determinations. The ligand field spectra of the hydroxocuprates(II) indicate tetragonally elongated CuO6-octahedra with very long axial distances. From the ESR investigations further conclusions can be drawn concerning structural differences between the Ba- and the Sr-compound [Sr2Cu(OH6)], the atomic parameters of which are still unknown.

PREPARATION AND LATTICE DISTORTION OF PEROVSKITE-TYPE COMPOUNDS A2+R4+O3 (A = Ba,Sr R = Ce,Pr,Tb)

Abstract Preparation and lattice distortion of perovskite-type compounds A2+R4+O3 were studied. All of them belong to the same lattice symmetry of orthorhombic Pbnm,that is,they have monoclinic perovskite cells. The magnitude of the monoclinic distortion increases mainly along the diagonal axis of the b-plane of the perovskite cell with the decrease of “tolerance factor”.

Raman spectra and vibrational assignments of aluminum borohydride and some isotopic derivatives

Raman spectra of the compounds A1(B 11H 4) 3, A1(B 10H 4) 3, Al(B 11D 4) 3 and A1(B 10D 4) 3 have been obtained for the pure liquids,and the frequencies assigned with the help of polarization measurements and the infrared frequencies in the literature. Although the evidence cannot be considered entirely conclusive, the assignment appears to confirm the prismatic bridge structure.