Crystal structure, phase stability, and electronic structure of Ti-Al intermetallics: TiAl3

The structural phase stability and electronic properties of the intermetallic compound TiAl3 are investigated with use of the self-consistent all-electron total-energy linear muffin-tin orbitals band-structure method within the local-density-functional approximation. The calculated equilibrium volumes have a Wigner-Seitz radius of 2.92 a.u. for the D022 and D019 structures, and 2.91 a.u. for the L12 structure, showing the expected consistency in the volume among the different structures. The calculated value also agrees with experiment for the D022 structure to within 2%. The calculated heats of formation are 0.42, 0.37, and 0.28 eV/atom for the D022, L12, and D019 lattices, respectively. The D022 structure is calculated to be the most stable phase, as observed experimentally. The calculated bulk moduli are 1.2, 1.5, and 1.1 Mbar for D022, L12, and D019, respectively. Among the three structures, the density of states at the Fermi energy, N(EF), is lowest in D022 and so is consistent with the inverse relation between N(EF) and stability found for other aluminum intermetallic compounds.