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1993 (2)
1Author    Ullrich PietschRequires cookie*
 Title    Static and Dynamical Valence-Charge-Density Properties of GaAs  
 Abstract    Owing to the close neighbourhood of Ga and As in Mendeleev's table, GaAs shows two funda-mental classes of X-ray structure amplitudes distinguished by their extremely different scattering power. They are differently sensitive to the valence electron density (VED) redistribution caused by the chemical bond and must be measured by different experimental methods. Using such data, both the VED and the difference electron densities (DED) are calculated here. Comparison with theoret-ical densities shows that the VED is characterized by covalent, ionic and metallic contributions. The DED constructed from GaAs and Ge data demonstrates the electronic response caused by a "protonic" charge transfer between both f.c.c. sublattices as well as the transition from a purely covalent to a mixed covalent-ionic bond. Especially the charge-density accumulation between nearest neighbours (bond charge (BC)) depends on the distance between the bonding atoms and changes under the influence of any lattice deformation. This phenomenon is described by a BC-trans-fer model. Its direct experimental proof is given by measuring the variation of the scattering power of weak reflections under the influence of an external electric field. This experiment demonstrates that the ionicity of the bond changes in addition to the BC variation. 
  Reference    Z. Naturforsch. 48a, 29—37 (1993); received December 5 1991 
  Published    1993 
  Keywords    Valence charge density, GaAs, Chemical bond, Bond charge transfer, Ionicity 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0029.pdf 
 Identifier    ZNA-1993-48a-0029 
 Volume    48 
2Author    Ryosei Uno, Haruo Ozawa, Jun Ishigaki, Ken YukinoRequires cookie*
 Title    Electron Distribution in Some Zincblende-Type Crystals  
 Abstract    The elctron density distribution in crystalline ZnSe and ZnTe has been measured by X-ray diffraction on powder samples and is compared with the results for other zincblende-type crystals. It is shown that the data for these two compounds corroborate the linear dependence on the bond charge that has been found earlier for the effective atomic charge from infrared reflection measure-ments, the optical dielectric constant and the ionicity estimated from pseudopotential band theory. 
  Reference    Z. Naturforsch. 48a, 38—40 (1993); received January 10 1992 
  Published    1993 
  Keywords    Zincblende-type crystals, Bond charge, Ionicity, X-ray powder diffraction, Electron density distribution 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0038.pdf 
 Identifier    ZNA-1993-48a-0038 
 Volume    48