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'Hydrogen Bond' in keywords Facet   section ZfN Section A:Volume 048  [X]
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1993 (2)
1Author    Ivar Olovsson, Halina Ptasiewicz-Bak, GarryJ. MclntyreRequires cookie*
 Title    Superposition and Polarization Effects on the Electron Density of Lone Pairs  
 Abstract    There appears to be conflicting experimental evidence on the redistribution of the electron density in the lone-pair and other regions of a molecule due to the interaction with its nearest neighbours. In some experimental as well as theoretical deformation density maps a decrease in the lone-pair density has been reported, whereas in other cases an increase has been found. It appears that two major, counteracting factors are responsible for these differences (apart from experimental errors in the diffraction studies and limited accuracy in the theoretical calculations): an increase in the lone-pair density is expected due to the polarizing influence of the neighbours, whereas simple superposition of the isolated monomer deformation densities will lead to an apparent decrease due to the overlap with the negative contours of the neighbouring atom. Depending on which of these factors is the dominant one, an increase or decrease may thus be observed. These points are illustrated by recent results on nickel sulfate hexahydrate and some other hydrogen-bonded compounds. The electron density based on the fitted deformation functions of all atoms in the structure is compared with the individual densities calculated from deformation functions of the separate monomers. In this way the effects of simple superposition of the individual densities have been studied, and a partitioning of the electrostatic and polarization contributions to the hydrogen bonds and other relatively weak bonds to the oxygen lone-pairs attempted. 
  Reference    Z. Naturforsch. 48a, 3—11 (1993); received January 30 1992 
  Published    1993 
  Keywords    Electron density, Superposition effects, Polarization effects, Lone pairs, Hydrogen bonds 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0003.pdf 
 Identifier    ZNA-1993-48a-0003 
 Volume    48 
2Author    B. N. Figgis, E. S. Kucharski, M. VrtisRequires cookie*
 Title    Spin Transfer through Hydrogen Bonding in [CO(NH 3 ) S (OH 2 )| |Cr(CN) 6 | ?  
 Abstract    A polarised-neutron diffraction experiment on [Co(NH 3) 5 (H 2 0)][Cr(CN) 6 ] shows the unexpected features of spin populations on the cobalt ((0.5(2) e) and the "ammine" hydrogen (0.8(1) e in total) atoms. A local density approximation DV-Xa calculation on a unit that models the molecular geometry in the crystal returns features that are broadly in agreement with the experiment. The calculation also reproduces the major features of a charge density experiment on the complex, including the low (+1.6 e) charges on the ions, in place of the formal ±3 e. 
  Reference    Z. Naturforsch. 48a, 123—126 (1993); received October 14 1991 
  Published    1993 
  Keywords    Spin density, Hydrogen bond, Local density approximation calculation, Charge den-sity, Spin transfer 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0123.pdf 
 Identifier    ZNA-1993-48a-0123 
 Volume    48