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Theory of divalent ions in crystals

Raghurama, G and Narayan, Ramesh (1983) Theory of divalent ions in crystals. In: Pramana, 21 (5). pp. 301-309.

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The divalent ions in alkaline earth chalcogenides are viewed as compressible objects and are treated within a purely ionic model. As in earlier studies on the alkali and ammonium halides, the ions are taken to be in the form of space-filling polyhedral cells and the compression energy, which is the source of repulsion, is written as a surface integral over the cell faces. A single method of computing the repulsion energy in any crystal lattice of arbitrary symmetry is proposed and the repulsion parameters B and a are refined for the divalent ions under study. The theory explains the predominant occurrence of the NaCl structure in the alkaline earth chalcogenides. Hard sphere radii are estimated for the tetravalent cations $Ti^{4+}$, $Sn^{4+}$ and $Pb^{4+}$ using the repulsion parameters of $0^{2-}$ ion and the data on the corresponding rutile structure oxides. These radii are seen to be consistent with the measured interionic distances in several compounds occurring in the perovskite structure. The free transfer of repulsion parameters among several structures, which is a key feature of the present approach to repulsion, is confirmed to be valid by the present study.

Item Type: Journal Article
Publication: Pramana
Publisher: Indian Academy of Sciences
Additional Information: Copyright of this article belongs to Indian academy of Sciences
Keywords: Divalent ions;Compressible ion theory;repulsion; Parameter;Hard sphere radii
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 04 Apr 2008
Last Modified: 19 Sep 2010 04:44
URI: http://eprints.iisc.ac.in/id/eprint/13614

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