NiTiSn a material of technological interest: Ab initio calculations of phase stability and defects

• Structural stability and electronic densities of state of NiTiSn has been studied.
• The phonon density of states has allowed to derive the Debye temperature of compound.
• We have obtained by ab-initio calculations the point-defect enthalpies of formation.
• The enthalpies of formation of defects have been calculated using large supercells.
• The most stable defects are Ni vacancies and Ni atoms in interstitial position.

First principles calculations of the structural, thermodynamic, electronic and vibrational properties of C1b-NiTiSn half-Heusler compounds have been performed. The enthalpy of formation of C1b-NiTiSn has been obtained. The phonon density of states has allowed to derive a value of the Debye temperature of the compound. The enthalpies of formation of point defects have been calculated using large supercells. Four sublattices have been introduced to account for the C1b structure and for the possibility of inserting atoms in the 4d Wyckoff positions of the F4−3m structure. The most stable defects are INi and VNi. The corresponding densities of states have been computed.