First-principles study of the martensitic transformation in pressure of the all-d-metal Heusler alloy Fe2NbIr.

• Soft modes and soft phonon behaviour leads to a change in phase stability. • Pressure-induced Fe 2 NbIr produces the pre-martensite phase. • This work presents an analysis of the pressure-induced martensitic transformat. The martensitic transformation of the new all- d -metal Heusler alloy Fe 2 NbIr is investigated using first-principles. The structure undergoes softening and hardening under pressure, which corresponds to the two phases of the martensitic phase transformation, i.e. C′ softening of the austenite and C′ hardening of the pre-martensite phase, implying that the pressure may induces to produce a cubic pre-martensite phase. An exciting phenomenon is found in the tetragonal deformation of the pre-martensite phase, where the pre-martensite phase overcome the energy barrier of the jump to produce a tetragonal martensite phase with a much lower energy. It explains the presence of a pre-martensite phase in shape memory alloys, i.e., it provides a conduit for the phase change. This work presents an analysis of the anomalous softening behaviour of Fe 2 NbIr and the mechanism of the pressure-induced martensitic transformation, and provides a new idea for study of the precursor effect of martensitic phase transformation. [ABSTRACT FROM AUTHOR]