Electronic structure, phase stability, and cohesive properties of Ti2XAl (X = Nb, V, Zr)

The self-consistent tight-binding linear muffin-tin orbital method was empl oyed to calculate the electronic structure and the total energy of Ti2XAl ( X = Nb, V, Zr) in B2, D0(19), and O (orthorhombic) phases and the results w ere used to study the phase stability and cohesive properties of these inte rmetallic compounds. Our theoretical calculation shows that the B2 phase is the most stable phase of Ti2NbAl as observed by experimentalists. However, the three phases are close in energy indicating the possibility of the pre sence of all these phases in equilibrium over a range of temperatures, whic h is in accordance with experimental observations. Our calculations predict that Ti2VAl is more stable in the B2 phase whereas Ti2ZrAl is more stable in the D0(19) phase. We also report the calculated equilibrium lattice para meters, cohesive energies, heats of formation, and bulk modulii of these sy stems, and a possible comparison of the calculated quantities with the avai lable experimental data is made. From our studies we are made to conclude t hat the concept of pseudogaps which has been very much emphasized for binar y intermetallics does not carry so much significance with respect to ternar y systems. [S0163-1829(99)05047-X].