Synthesis, and single-crystal X-ray diffraction and computational studies were carried out for the title compound. LaNiGe2 crystallizes in the orthorhombic lattice Cmcm (a = 4.3040(6) Å, b = 16.892(10) Å, c = 4.2367(5) Å, Z = 4). It consists of a Ni-capped Ge square lattice and Ge zigzag chains. A unique structural feature is the formation of the square lattice by the more electronegative Ge instead of by Ni atoms as in several other phases such as La3Ni4Ge4. Computational analysis indicates that the Ge square lattice acts as an electron donor while the Ge zigzag chain acts as electron acceptor. A donor−acceptor interaction similar to that in the CaBe2Ge2 phase stabilizes the Ge square lattice.

A new ternary chromium sulfide, BaCrS(2), was synthesized. This solid state compound crystallizes in the orthorhombic, centrosymmetric space group Pmmn (No. 59) with a = 4.2606(6) Å, b = 4.7944(7) Å, c = 9.443(1) Å, V = 192.89(5) Å(3), and Z = 2. The solid is similar to a previously known structure BaNiS(2) in which the Ni atom is coordinated to five sulfur atoms in a square pyramidal fashion. In BaCrS(2), the square pyramid distorts such that the two S(basal)-Cr-S(basal) angles are no longer equal. Thus the BaCrS(2) solid is orthorhombic whereas BaNiS(2) is tetragonal. The distortion from the square pyramidal coordination in the title compound is traced to the broken degeneracy of the d(xy)() and d(xz)() set by a computational analysis.

Resonance scattering was applied for the first time to the class of solids with the AB2X2 stoichiometry. A few members of this family seem to violate the developed rules describing the structure−property relationship, and the source of ambiguity is often the experimental determination of the structure itself. As an example, the newly synthesized BaZn2Ge2 can in principle adopt either the ThCr2Si2 or the CaBe2Ge2 type structures, and conventional diffraction techniques do not allow discrimination between the two structure models. The resonance scattering method shows, however, that BaZn2Ge2 crystallizes in the ThCr2Si2 structure (tetragonal I4/mmm; a = 4.527(2) Å c = 10.555(3) Å, Z = 2), in agreement with theoretical analyses.

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Bonding and Interlayer Charge Transfer in the Solid State Compound Na1. 9Cu2Se2Cu2O. -As revealed from extended Hueckel tight-binding calculations, in the Na-deficient title compound consisting of anti-CuO2 type Cu2O layers with square-coordinated O atoms, anti-PbO type Cu2Se2 layers and cationic Na layers, charge transfer proceeds mainly from the Na to the Cu2Se2 layer. Due to the higher Fermi level in the Cu2Se2 layer, the holes created by the incomplete occupancy of Na sites are located in this layer. -(CHACON, G.; LONG, X.; ZHENG, C.; J.