Revisiting the Phase Stability in Ni-X (X=Mo, Ti, In) Systems Using Ab Initio Calculations

In this paper, we report a theoretical prediction of the low-temperature phase diagrams for the Ni-Mo, Ni-Ti and Ni-In binary systems using ab initio evolutionary methodology. Our study uncovers two previously unreported intermetallic compounds that are thermodynamically stable at low temperatures: orthorhombic Ni₂Mo with Cmcm symmetry and tetragonal NiTi₂ with I4/mmm symmetry. Ni₂Mo and NiTi₂ will transform from their zero temperature ground state structures into their experimentally observed high temperature polymorphs above a critical temperature of 466 and 912 K, respectively. Finally, our DFT calculations with both PBE and LDA functional indicate that the experimentally observed Ni₃In, Ni₂In and Ni₁₃In₉ structures are all not stable at low temperature. Furthermore, no Ni₃In and Ni₂In structures that are stable at T = 0 K can be identified by our evolutionary search.