Welf Bronger Prof. Dr

Publications (3)0 Total impact

• Article: On the Volume Chemistry of Solid Compounds: the Legacy of Wilhelm Biltz

  Alexey Baranov, Miroslav Kohout, Frank R. Wagner, Yuri Grin, Rüdiger Kniep, Welf Bronger Prof. Dr
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  ABSTRACT: For the calculation of the atomic or ionic volumes the Quantum Theory of Atoms In Molecules method was applied. The regions (basins) around the nuclei confined by the zero-flux surfaces in the electron density gradient are called QTAIM atoms. They are non-overlapping and completely fill the space. The volume of the basins gives volumes of atoms or ions. The integration of the electron density within the volumina yields effective charges, defining neutral or ionic character of the given QTAIM species. Present investigations refer to metal hydrides, metal nitrides and to intermetallic compounds of the system Al-Pt. A linear relation between the ionic volumina of hydrogen or nitrogen established according to QTAIM and after Biltz has been found with (homodesmic) binary metal hydrides and binary metal nitrides, but has been observed merely as a trend with stronger deviations for heterodesmic compounds, such as ternary hydrido- and nitridometallates Aa[MmXx] (A – alkali or alkaline earth metal, M – transition metal and X – H or N). The deviation from linearity for heterodesmic compounds is caused by the different kinds of chemical bonds being present within the [MmXx] anions on the one hand and between the anions and the cations on the other hand reflected by the calculated volumes and the QTAIM charges of M and X components. Concerning the intermetallic compounds of the system Al-Pt, the quantum chemical calculations reveal negative charges for the platinum atoms and positive ones for the aluminium atoms in accordance with their electronegativities. Introducing the variation of the atomic volume with the composition extends the Vegard's approach and gives a non-linear slope for the concentration dependence of mean atomic volume which explains qualitatively the experimental results.
  Zeitschrift für anorganische Chemie 11/2008; 634(15):2747 - 2753.
• Article: Atomvolumina und Ladungsverteilungen in Nitridometallaten

  Welf Bronger Prof. Dr, Alexey Baranov, Frank R. Wagner, Rüdiger Kniep Prof. Dr
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  ABSTRACT: Atom Volumina and Charge Distributions in NitridometalatesThe linear relation between the nitride volumina calculated by use of the QTAIM-method developed by Bader and those derived from the tables of volume increments reported by Biltz does not hold for nitridometalates Aa[MmNn] (A = alkali or alkaline earth metal, M = transition metal). The clear deviation from linearity is caused by the different kinds of chemical bonds being present within the complex [MmNn] anions on the one hand and between the complex anions and the cations on the other hand. The significant covalency of the chemical bonds within the complex [MmNn] anions is reflected by the calculated volumina and the charge distributions between the M and N atoms using the Bader method. By comparing the oxidation numbers of the atoms forming the complex anions with their calculated charge assignments (QTAIM method) a significant charge reduction becomes evident.
  Zeitschrift für anorganische Chemie 10/2007; 633(15):2553 - 2557.
• Article: Zur Raumchemie des Wasserstoffs in binären und ternären Metallhydriden

  Welf Bronger Prof. Dr, Rüdiger Kniep Prof. Dr, Miroslav Kohout Dr
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  ABSTRACT: Die aus den Strukturen binrer und ternrer Metallhydride ermittelten Rauminkremente der Hydridionen nach W. Biltz sowie die auf quantenmechanischer Grundlage berechneten Volumina nach R. F. W. Bader und nach der ELF-Methode erlauben im gegenseitigen Vergleich Einblicke in die Bindungsverhltnisse. Es ergibt sich eine deutliche Abhngigkeit des Volumens des stark polarisierbaren Hydridions von den Bindungspartnern. In den salzartigen Verbindungen findet man die höchsten Volumenwerte, in den metallischen Systemen die niedrigsten. Beim Einbau von Wasserstoff in metallische Stoffe wie LaH2 oder Pd ist über ELF-Rechnungen eine Abhngigkeit der Struktur und Zusammensetzung der Einlagerungsverbindung von der Bindungsstruktur des Wirtsgitters zu erkennen.Volume Chemistry of Hydrogen in Binary and Ternary Metal HydridesA comparison of the concept of volume increments created by W. Biltz with those based on quantum mechanical calculations of the electron density (R.F.W. Bader) and ELF was performed for crystal structures of binary and ternary metal hydrides. The mutual comparison of the three methods permits insights into the bonding relationships of these compounds and reveals the considerable range of volume demand of a strongly polarisable bonding partner, such as the hydride ion. The highest values of volume increments are found in the saltlike hydrides, the lowest in the metallic compounds. Moreover the ELF analysis shows a relation between localizability of electrons in the host lattice and the structure and composition of the interstitial compound formed when hydrogen is inserted in metallic materials like LaH2 or Pd.
  Zeitschrift für anorganische Chemie 02/2005; 631(2‐3):265 - 271.