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1Author    Z. Akdeniz, M. P. TosiRequires cookie*
 Title    Ionic Conduction and Molecular Structure of Molten FeCl 3  
 Abstract    Former experiments on molten FeCl 3 have shown that, as for A1C1 3 , melting is accompanied by a transition from sixfold to essentially fourfold coordination. However, in contrast to AICI3, the FeCl 3 melt near freezing has an appreciable ionic conductivity. We propose a model for the structure of FeCl 3 melt as consisting of closely packed Fe 2 Cl 6 bitetrahedral molecules in equilibrium with (Fe 2 Cl 5) + and (Fe 2 Cl 7)" ionised species. 
  Reference    Z. Naturforsch. 53a, 960—962 (1998); received November 18 1998 
  Published    1998 
  Keywords    Melting, Liquid Structure, Molecular Liquids 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0960.pdf 
 Identifier    ZNA-1998-53a-0960 
 Volume    53 
2Author    G. Abed, SalimM. KhalilRequires cookie*
 Title    Amel  
 Abstract    MINDO-forces calculations have been performed on the uncatalysed and acid-catalysed Friedel-Crafts reaction between CH 3 F and CH 4 . It has been found that the catalysed reaction is exothermic, spontaneous and has a smaller potential-energy barrier than the uncatalysed reaction. The mechanisms for uncatalysed and catalysed reactions are discussed. 
  Reference    Z. Naturforsch. 54a, 251—255 (1999); received December 22 1998 
  Published    1999 
  Keywords    Melting, Liquid Structure, Molecular Liquids 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0251.pdf 
 Identifier    ZNA-1999-54a-0251 
 Volume    54 
3Author    S. Itoh, M. Konagai, K. TakahashiRequires cookie*
 Abstract    The structural and dynamic properties of molten lithium iodide are investigated at two pressures (334 MPa at 784 K and 1054 MPa at 915 K), using molecular dynamics simulations with Born-Mayer-Huggins type pair potentials. On increasing the pressure, the local packing of the ions changes from tetrahedral to octahedral, the self-exchange velocity in the coordination shells decreases by a factor of 0.031, Du by a factor of 0.033 and D, by a factor of 0.021. M o le c u la r D y n a m ic s S tu d y o f M o lte n L ith iu m Io d id e 
  Reference    Z. Naturforsch. 46a, 155 (1991); received February 15 1990 
  Published    1991 
  Keywords    Molecular dynamics, Liquid structure, Lil, Lithium iodide, Pressure 
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 TEI-XML for    default:Reihe_A/46/ZNA-1991-46a-0155.pdf 
 Identifier    ZNA-1991-46a-0155 
 Volume    46 
4Author    Z. Akdeniz, M. P. TosiRequires cookie*
 Title    A Refined Ionic Model for Clusters Relevant to Molten Chloroaluminates  
 Abstract    A model of ionic interactions in neutral and ionized aluminium trichloride clusters, which accounts for ionic deformability through (i) effective valences and (ii) electrostatic and overlap polarizabilities, is evaluated for applications to classical simulation studies of the pure melt and of molten alkali chloroaluminates. The disposable parameters in the model are determined from the measured values of the bond length in the (A1C1 4)~ molecular ion and of an Al-Cl bond length and a vibrational frequency in the A1 2 C1 6 molecular dimer. The model is tested against the remaining available data from experiment and from quantum chemical calculations on molecular bond lengths, bond angles and vibrational frequencies for A1 2 C1 6 , (A1C1 4)~ and (A1 2 C1 7)~ clusters. Structural and dynamical properties are also evaluated for the (A1 2 C1 5) + , A1C1 3 and (A1C1 2) + clusters. The results for the energetics of dissociation, ion transfer and isomer excitation reactions are compared with as yet unpublished data obtained by P. Ballone in first-principles calculations by a density functional method. The overall quality of the tests supports the approximate validity and transferability of the model. 
  Reference    Z. Naturforsch. 54a, 180—186 (1999); received February 17 1999 
  Published    1999 
  Keywords    Ionic Clusters, Liquid Structure, Molten Salts 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0180.pdf 
 Identifier    ZNA-1999-54a-0180 
 Volume    54 
5Author    Z. Akdeniz, M. P. TosiRequires cookie*
 Title    Structure and Energetics of Clusters Relevant to Thorium Tetrachloride Melts  
 Abstract    We study within an ionic model the structure and energetics of neutral and charged molecular clusters which may be relevant to molten ThCl 4 and to its liquid mixtures with alkali chlorides, with reference to Raman scattering experiments by Photiadis and Papatheodorou. As stressed by these authors, the most striking facts for ThCl 4 in comparison to other tetrachloride compounds (and in particular to ZrCl 4) are the appreciable ionic conductivity of the pure melt and the continuous structural changes which occur in the melt mixtures with varying composition. After adjusting our model to data on the isolated ThCl 4 tetrahedral molecule, we evaluate (i) the Th 2 Cl 8 dimer and the singly charged species obtained from it by chlorine-ion transfer between two such neutral dimers; (ii) the ThCl 6 and ThCl 7 clusters both as charged anions and as alkali-compensated species; and (iii) various oligomers carrying positive or negative double charges. Our study shows that the characteristic structural properties of the ThCl 4 compound and of the alkali-Th chloride systems are the consequence of the relatively high ionic character of the binding, which is already evident in the isolated ThCl 4 monomer. 
  Reference    Z. Naturforsch. 55a, 772—778 (2000); received August 13 2000 
  Published    2000 
  Keywords    Ionic Clusters, Liquid Structure, Molten Salts 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0772.pdf 
 Identifier    ZNA-2000-55a-0772 
 Volume    55 
6Author    O. Akinlade, Z. Badirkhan3, G. PastorebRequires cookie*
 Title    Thermodynamics and Structure of Liquid Metals from a New Consistent Optimized Random Phase Approximation  
 Abstract    We study thermodynamics and structural properties of several liquid metals to assess the validity of the generalized non-local model potential (GNMP) of Li et al. [J. Phys. F16, 309 (1986)]. By using a new thermodynamically consistent version of the optimized random phase approx­ imation (ORPA), especially adapted to continuous reference potentials, we improve our previous results obtained within the variational approach based on the Gibbs -Bogoliubov inequality. Hinging on the unified and very accurate evaluation of structure factors and thermodynamic quantities provided by the ORPA, we find that the GNMP yields satisfactory results for the alkali metals. Those for the polyvalent metals, however, point to a substantial inadequacy of the GNMP for high valence systems. 
  Reference    Z. Naturforsch. 56a, 605—612 (2001); received March 1 2001 
  Published    2001 
  Keywords    Liquid Metals, Liquid Structure, ORPA, Pseudopotentials, Thermodynamics 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0605.pdf 
 Identifier    ZNA-2001-56a-0605 
 Volume    56 
7Author    Z. Akdeniza, M. P. TosiaRequires cookie*
 Title    Structure and Binding of Ionic Clusters in Th and Zr Chloride Melts  
 Abstract    We discuss microscopic ionic models for the structure and the binding of small clusters which may exist as structural units in molten ThCl4 and ZrCl4 and in their mixtures with alkali halides according to Raman scattering studies of Photiadis and Papatheodorou. The models are adjusted to the two isolated tetrahedral molecules. Appreciably higher ionicity is found for ThCl4 than for ZrCl4, and this fact underlies the strikingly different behaviour of the two systems in the dense liquid state -in particular, a molecular-type structure for molten ZrCl4 against a structure including charged oligomers in molten ThCl4. 
  Reference    Z. Naturforsch. 56a, 717—720 (2001); received September 10 2001 
  Published    2001 
  Keywords    Ionic Clusters, Liquid Structure, Molten Salts 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0717.pdf 
 Identifier    ZNA-2001-56a-0717 
 Volume    56 
8Author    T. Radnai, H. OhtakiRequires cookie*
 Title    Intramolecular and Liquid Structures of Tetramethylurea Studied by Means of X-Ray Diffraction  
 Abstract    The intramolecular and liquid structures of tetramethylurea (TMU) were investigated by the liquid x-ray diffraction method. It is confirmed that in the liquid state the four methyl groups are out of the plane which is constructed by the O, C, and the two N atoms, the molecular structure being similar to what had been found in the gas phase. All structural parameters are in good agreement with those of TMU determined in the gas phase and with those of amide derivatives in the liquid phase. The liquid is characterized by a random distribution of molecules as predominant, but a weak molecular ordering characterized by approximately two intermolecular nonbonding Me • • • O dis-tances at 340 pm is proposed. 
  Reference    Z. Naturforsch. 47a, 1003—1010 (1992); received May 20 1992 
  Published    1992 
  Keywords    Tetramethylurea, Liquid x-ray diffraction, Liquid structure, Molecular structure, Non-aqueous solvent 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-1003.pdf 
 Identifier    ZNA-1992-47a-1003 
 Volume    47