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Electron Poor Materials Research Group EPM RG

Electron Poor Materials Research Group EPM RG. Central idea Complex structured semiconductors from “diluting” the abrupt metal-nonmetal transition in the Periodic Table when going from group III (13) to group IV (14) elements. b -SiB 3. Central questions:

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Electron Poor Materials Research Group EPM RG

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  1. Electron Poor Materials Research Group EPMRG

  2. Central idea Complex structured semiconductors from “diluting” the abrupt metal-nonmetal transition in the Periodic Table when going from group III (13) to group IV (14) elements b-SiB3 Central questions: What are (feasible) compositions, structures, bonding motifs (mechanisms of band gap opening) of such semiconductors? Properties?

  3. Refractory semiconductors (boron, (B-C), B-Si, B-Ge) Larger band gaps (> 1 eV) Thermoelectric semiconductors (Zn-Sb, Al-Si, Al-Ge) Narrow band gaps (< 0.5 eV) Common features: complex crystal structures (various forms of disorder, large unit cells) → low (lattice) thermal conductivity

  4. Electron poor bonding patterns Charge density/bonding analysis Boron: bonding patterns, ground state? g-B28 High pressure modification (Dubrovinski, van Smaalen) a-B12 (not completely conclusive) b-boron (disordered) Synthesis of a and b-boron crystals by using metal fluxes (Pt, Pd, Ni) Low temperature crystallization of b-boron?

  5. ZnSb Zn2Sb2 rhomboid ring: multi center bonded entity (4e4c) B-Si b-SiB3 Si42+ B122-

  6. B-Ge empty B-Si b-SiB3 a-SiB3 Disordered, complex SiB6 Al-Si Al-Ge empty empty, but metastable phases are known

  7. Theory • Modeling of B-C, B-Si, B-Ge, Al-Si, Al-Ge systems • Polarity of frameworks, quantification of polarity, distinction to Zintl phases? Zn-Sb Zn-Te Zn-Se Mg-Sb Li-Sb • Support of experimental bonding (charge density) analysis • Modeling of properties • Universal transition (structures & bonding patterns) between group 13&14?

  8. Old (and safe) stuff: • Zn5Sb4In2: high temperature structures and properties • ZnSnSb2-2InSb: detailed property determination around MI transition

  9. New synthesis activities Everything leading to new III-IV combinations • Oxidation of Zintl phases • Hydrogenations • HCl, Cl2, Br2, I2 • (ionic liquids) • amalgamations • NaSi, NaGe, NaSn • LiSi, LiGe, Li7Ge12 • LiBC • Li-Al-Si, Li-Al-Ge • Li(A)-B-Si, Li(A)-B-Ge (Hillebrecht) High-pressure B-Si, B-Ge

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