ISSN:
0570-0833
Keywords:
Intermetallic phases
;
Atomic radii
;
Description of structure
;
Computer graphics
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Metallic radii, which are obtained from atomic distances in the pure elements, are generally used for the calculation of distances in intermetallic compounds. However, the procedure for using such radii depends on the individual structural type: (a) For high coordination numbers and only slightly differing distances between atoms of the same kind and different atoms, all distances in a structure are proportional to the sum of radii, weighted according to the compositon. Such a “Vegard” relationship for ordered compounds is obeyed by intermetallic compounds with topological close packings, but strictly only if the various kinds of distances are correlated via symmetry relationships. For compounds with low coordination numbers the simple sum of radii holds for atoms participating in the shortest bond (e.g. in ionic crystals).-(b) The number of neighbors determines the size of each atom. It can be shown that the bond strength-bond length concept, developed for valence compounds, and often dealt with in the literature over the last ten years, is also applicable for alloys. On this basis a formalism is developed which uniformly describes the size of the atoms as a function of the coordination number for both the limiting cases of multiple bonds in molecules and for close packed atomic arrangements in alloys.
Additional Material:
21 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/anie.198300951
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