First-principles investigation on stability and oxygen adsorption behavior of a O/B2 interface in Ti₂AlNb alloys

This work studied the stability and oxygen adsorption properties of interface between the O and B2 phases in Ti₂AlNb alloys by first principles calculations. In term of their crystal structures, the connection between O(11‾0) and B2(211‾) slabs owns the minimum lattice mismatch, which was therefore built up as the O/B2 interface. Through a serious examination including the influences of terminal elements and relative positions on the stability of the interface, a HCP stacking, that the interfacial atoms of O phase are located at the top of the atoms in the second layer of B2 phase, was clarified as the most coherent interface between O(11‾0) and B2(211‾) slabs. Adsorption of oxygen atom in the interface was studied and the estimated adsorption energies show that this process is thermodynamically stable, but less stable than that on the O(010) surface, illustrating that the O/B2 coherent interface without defects has limited influence on the oxidation of Ti₂AlNb alloys.