Exploratory synthesis in the K-In-Ge-As system has yielded the unusual layered compounds K8In8Ge5As17(1) and K5In5Ge5As14(2), both of which contain In-Ge-As layers with interleaved potassium ions, Ge-Ge bonds, InAs4tetrahedra, As-As bonds, and rows of Ge2As6dimers. Compound 1 has As3groups, while compound 2 has infinite As ribbons on both faces of each layer. Unlike compound 1, compound 2 has substitutional defects where indium partially occupies each of the three independent germanium sites in the ratio of 1:5 for In:Ge. This partial occupancy makes 2 an electron-precise compound. The Ge(In)-Ge(In) bond of 2 is longer than the Ge-Ge bond of 1, and this bond lengthening effect was confirmed by performing DFT-MO calculations on the model compounds H3Ge-GeH3and H3Ge-InH-3. Possible implications of electron imprecise formulas determined by X-ray crystal structure determinations are discussed. Compound 1: space groupP21/cwitha=18.394 (8) Å,b=19.087 (7) Å,c=25.360 (3) Å,β=105.71 (2)°,V=8571 (4) Å3, andDcalcd=4.45g/cm3forZ=4. Refinement on 4455 reflections yieldedR(Rw)=6.8%(7.8%). Compound 2: space groupC2/mwitha=40.00 (1) Å,b=3.925 (2) Å,c=10.299 (3),β=99.97 (2)°,V=1592 (1) Å3, andDcalcd= 4.55g/cm3forZ=8. Refinement on 1206 reflections yieldedR(Rw)=5.6% (5.7%).
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry