Structural, elastic and electronic properties of equiatomic PtTi as potential high-temperature shape memory alloy

We investigated the phase stability from B2 to L10/B19/B19′ in equiatomic PtTi alloy using the density functional theory within the generalized gradient approximation. Their structural, energetic, electronic and the mechanical properties were determined to show the stability trend of the shape memory binary alloy. The lattice parameters are well reproduced and agree to within 2% with the available experimental data. We found that the calculated heats of formation and density of states predicted B19 and B19′ PtTi to be the most stable structures compared to B2 and L10. On the other hand, their mechanical stability predictions show consistency with regard to the elastic constants and phonon dispersion curves. The elastic instability (negative Cij) and soft modes were observed in the B2, B19 and B19′ structures and not found in the L10 structure.

► Good predictions of the structural and thermodynamic properties at 50 at.% Pt.
► B2 is vibrational unstable due to presence of imaginary modes, while L10 is not.
► B2 instability as compared to B19/B19′ and L10 phases due to higher states at Ef.
► The predicted decreasing order in the stability trend is B19 > B19′ > L10 > B2.