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

The structural phase stability and electronic properties of the intermetallic compound ${\mathrm{TiAl}}_3$ 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 D$0_{22}$ and D$0_{19}$ structures, and 2.91 a.u. for the L$1_2$ structure, showing the expected consistency in the volume among the different structures. The calculated value also agrees with experiment for the D$0_{22}$ structure to within 2%. The calculated heats of formation are 0.42, 0.37, and 0.28 eV/atom for the D$0_{22}$, L$1_2$, and D$0_{19}$ lattices, respectively. The D$0_{22}$ 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 D$0_{22}$, L$1_2$, and D$0_{19}$, respectively. Among the three structures, the density of states at the Fermi energy, N(${\mathit{E}}_{\mathit{F}}$), is lowest in D$0_{22}$ and so is consistent with the inverse relation between N(${\mathit{E}}_{\mathit{F}}$) and stability found for other aluminum intermetallic compounds.