ON THE PHASE-STABILITY OF TRANSITION-METAL TRIALUMINIDE COMPOUNDS

An ab-initio total energy and electronic structure calculation has bee n performed for Al13Ru4 compound with the Al13Fe4 structure type. It i s found to be more stable than the earlier predicted DO22 structure fo r the exact 3:1 stoichiometric ruthenium trialuminide Al3Ru. Using a ' frozen-potential' method the relative structural stability of the Al3F e4 DO22 and Ll(2) structure types is studied as a function of electron concentration. In particular, it is shown that the Al13Fe4 structure is predicted correctly for the group 8 transition metals whereas there is a strong stability of the DO22 structure for group 5. The trends i n structural stability are interpreted directly in terms of the shape of the densities of states.