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1Author    FrancisJ. BartisRequires cookie*
 Abstract    This problem is reconsidered in the light of the mounting evidence that dislocations act as the centres of nucleation and growth. A new relation between the fraction of the sample in liquid form and the equilibrium temperature is derived and found to fit well the data on succinonitrile and N-p-ethoxybenzylidene-p'-butylaniline (EBBA). It is argued that the additional dislocations in a cyclopentyl-l-thiaethane sample after rapid crystallization are responsible for the greater breadth of its melting transition compared to that of the same sample following slow crystallization. Past studies of the fractional melting process are criticized for their failure to include the early stages of the transition in their comparison of theory and experiment. C o u r s e o f th e M e ltin g T r a n s itio n in O r g a n ic C o m p o u n d s 
  Reference    Z. Naturforsch. 46a, 630—634 (1991); received March 31 1990 
  Published    1991 
  Keywords    Melting, Latent heat, Organic compounds, Dislocations, Impurities 
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 TEI-XML for    default:Reihe_A/46/ZNA-1991-46a-0630.pdf 
 Identifier    ZNA-1991-46a-0630 
 Volume    46 
2Author    StadeS. Nunes, S. Sulaiman, N. Sahoo, T. P. Das, M. Frank, W. Kreische, K. B. NielsenRequires cookie*
 Title    Study of the Location of Implanted Fluorine Atoms in Silicon and Germanium through Their Nuclear Quadrupole Interactions  
 Abstract    Time Differential Perturbed Angular Distribution (TDPAD) measurements of the nuclear quadrupole hyperfine parameters for 19 F* implanted into amorphous, polycrystalline and crys-talline silicon and germanium are reported and reviewed. Two signals are observed in the crystalline materials (« 35 and 23 MHz in silicon, % 33 and 27 MHz in germanium) while only one is detected in the amorphous and polycrystalline samples (ä22 MHz in silicon, «27 in germanium). Impurity sites in these materials were modeled using a Hartree-Fock cluster procedure. The Intrabond, Antibond, and Substitutional sites in the bulk were studied in both silicon and germanium. The ATOP and Intrabond Surface sites were also studied in silicon and the results extended to germa-nium. Lattice relaxation effects were incorporated by employing a geometry optimization method to obtain minimum energy configurations for the clusters modelling each site. The electronic wave functions were obtained for each optimized cluster by applying Unresctricted Hartree-Fock theory, and these wave functions were used to calculate the nuclear quadrupole hyperfine parameters at the site of the fluorine nucleus. Comparison of the theoretical hyperfine parameters to the experimental values indicates that 19 F* located in the Intrabond and Intrabond surface sites could readily explain the higher frequency signal that has been observed. 19 F* in the Antibond and the surface ATOP sites yield hyperfine parameters consistent with the low frequency signal observed in the crystalline materials and the single signal observed in the amorphous (or polycrystalline) materials. Examina-tion of these two sites, in view of other available experimental evidence including the temperature dependence of the TDPAD signals, leads to the conclusion that the lower frequency signal is due to 19 F* implants which have come to rest at the site of dangling bonds in the bulk. These dangling bonds are created as a result of damage generated in the individual collision cascades during the implantation process. 
  Reference    Z. Naturforsch. 51a, 560—564 (1996); received December 12 1995 
  Published    1996 
  Keywords    Semiconductors, Impurities, Electronic structure, Hartree-Fock, Electric field gradient 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0560.pdf 
 Identifier    ZNA-1996-51a-0560 
 Volume    51 
3Author    F. Köksal, İ. Kartal, B. KarabulutRequires cookie*
 Title    Electron Paramagnetic Resonance of Cu 2+ in KHC0 3 Single Crystals  
 Abstract    The electron paramagnetic resonance spectra of Cu 2+ doped KHC0 3 single crystals were studied at room temperature. The results indicate a substitutional entrance of the Cu 2+ ions in place of the magnetically inequivalent K + sites. The charge compensation is supposed to be fulfilled by proton vacancies. The hyperfine lines were well resolved and the 65 Cu hyperfine coupling tensors were also found. The ground state of Cu 2+ indicates the dominance of the d x i_ y 2 orbital and, therefore, elongation of the polyhedron, similar to a lengthened octahedron. 
  Reference    Z. Naturforsch. 54a, 177—179 (1999); received January 9 1999 
  Published    1999 
  Keywords    EPR, Cu 2+, Potassium Bicarbonate, Crystal Field, Substitution, Impurity 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0177.pdf 
 Identifier    ZNA-1999-54a-0177 
 Volume    54 
4Author    Ho Choh, JaeKap JungRequires cookie*
 Title    Sung  
 Abstract    External influences on the 14 N NQR of ferroelectric NaN0 2 , such as changes of the temperature, electric field, stress, gamma-ray irradiation, and impurity doping are reviewed. They normally cause either a frequency shift or a broadening of the 14 N NQR lines and are strongly related to the change of the spontaneous polarization. 
  Reference    Z. Naturforsch. 55a, 124—128 (2000); received August 23 1999 
  Published    2000 
  Keywords    l4 N NQR, Ferroelectric NaN0 2, Spontaneous Polarization, External Effects, Impurity 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0124.pdf 
 Identifier    ZNA-2000-55a-0124 
 Volume    55