Site preference and phase stability of Ti doping Ni–Mn–Ga shape memory alloys from first-principles calculations

• Site preference and phase stability of NiMnGaTi are studied by first-principles.
• The Ti atoms prefer to occupy the Ga sites in the Ni2MnGa austenitic phase.
• The phase stability becomes worse when Ga is replaced by Ti.
• The phase stability is discussed based on the densities of states.

The effects of Ti content on martensitic transformation and phase stability of Ni50Mn25Ga25−xTix shape memory alloys were investigated from first-principles calculations based on density functional theory. The formation energy results indicate that the added Ti preferentially occupies the Ga sites in Ni2MnGa alloy due to the lowest formation energy. The total energy difference between austenite and martensite increases with Ti alloying, being relevant to the experimentally reported changes in martensitic transformation temperature. The phase stability of Ni50Mn25Ga25−xTix austenite decreases with increasing Ti content, which results from the reduced Ni 3d–Mn 3d hybridization when Ga is replaced by Ti.