A potentially useful high-temperature intermetallic compound Ti3Al is investigated theoretically by the self-consistent linear muffin-tin orbitals (LMTO) and full-potential linearized augmented-plane-wave (FLAPW) methods within the local-density approximation. Structural properties were calculated for the naturally observed structure, D019, and for two other similar structures, D022 and L12. The LMTO-calculated Wigner-Seitz radii are 2.98 a.u. for all three structures, in excellent agreement with the experimental value (2.99 a.u.) of the observed D019 structure, while the values from the FLAPW method are 2.94 a.u. for the three structures, showing an agreement within about 2%. The calculated formation energies are 0.29, 0.27, and 0.29 eV/atom by the LMTO, and 0.28, 0.25, and 0.27 eV/atom by the FLAPW for the D019, D022, and L12 structures, respectively. The calculated bulk moduli are 1.2 Mbar for all the phases done by the LMTO and FLAPW except the D019 phase from the LMTO calculations, where the value is 1.3 Mbar. These calculated formation energies and bulk moduli agree well (to 10%) with experimental data. The FLAPW-calculated c/a ratio for the D019 and D022 structures are 0.807 and 2.131, respectively. The value for the D019 structure is within 1% of the observed value (0.8007) and the value for the D022 structure is significantly lower than the observed value (2.234) for TiAl3. Charge-density plots for D019 and L12 show quite localized charge distributions in both phases. The covalent character of the bonding is not significant, which may be a good sign for ways to improve its poor ductility.
ASJC Scopus subject areas
- Condensed Matter Physics