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Relative stability of LI2, DO22, and DO23 structures in MAl3 compounds

Published online by Cambridge University Press:  31 January 2011

A. E. Carlsson
Affiliation:
Department of Physics, Washington University, St. Louis, Missouri 63130
P. J. Meschter
Affiliation:
McDonnell Douglas Research Laboratories, P. O. Box 516, St. Louis, Missouri 63166
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Abstract

The structural energy differences between cubic LI2 and tetragonal DO22 crystal structures are calculated for MAl3 compounds, where M is a group III, IV, or V transition metal. The stability of the DO22 structure relative to L12 increases rapidly as the transition-metal d-electron count increases. Typical values of E(DO22) – E(L12) are 0.1–0.15 eV/atom (9600–14500 J/g-atom) for group III,  0.05 eV/atom ( 4800 J/g-atom) for group IV, and ∼ –0.2 eV/atom (∼ –19000 J/g-atom) for group V trialuminides. Similar trends are calculated for the DO23/L12 energy difference. The calculated electronic densities of states (DOS) show that each structure has a minimum in the DOS distribution at a characteristic d-electron count. The preferred crystal structure for a given compound is the one in which the Fermi level lies in the minimum.

Type
Rapid Communications
Copyright
Copyright © Materials Research Society 1989

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References

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