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

Abstract

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.