Theoretical and Experimental Study of Relaxations in Al3Ti and Al3Zr Ordered Phases

The aim of the present investigation was to elucidate the role of structural relaxations in determining the relative stability of L12, D022, and D023 structures in Al3Ti and Al3Zr. This task was accomplished by a unique combination of total-energy electronic structure calculations and (for Al3Zr) high resolution neutron diffraction with Reitveld refinement. Calculated and measured atomic displacements are in excellent agreement. Local relaxation is found to be responsible for the stability of the D023 structure in Al3Zr, in agreement with experimental evidence.