Standard enthalpies of formation of selected Ni2YZ Heusler compounds

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The standard enthalpies of formation (ΔfH°) of selected ternary Ni-based Heusler compounds Ni2YZ (Y = Co, Cu, Fe, Hf, Mn, Ti, V; Z = Al, Ga, In, Si, Ge, Sn) were measured using high temperature direct reaction calorimetry. The measured standard enthalpies of formation (in kJ/mole of atoms) of the Heusler structured (L21, prototype Cu2MnAl, Pearson symbol cF16, space group Fm3(_) m) compounds are: Ni2MnGa (−29.8 ± 3.9); Ni2MnIn (−24.5 ± 2.0); Ni2MnSn (−29.7 ± 2.9); Ni2TiGa (−42.5 ± 2.2); Ni2TiIn (−28.5 ± 1.1); Ni2TiSn (−46.8 ± 2.0), for the B2 compound (prototype CsCl, Pearson cP2, space group Pm3(_) m): Ni2MnAl (−32.0 ± 2.8), for the inverse Heusler structured (i-L21, prototype Li2AgSb, Pearson symbol cF16, space group F4(_) 3 m) compound: Ni2CuSn (−12.5 ± 2.1), for the compounds of the L12 (prototype AuCu3, Pearson symbol cP4, space group Pm3(_) m) structure: Ni2CuAl (−38.9 ± 3.1); Ni2FeGe (−25.8 ± 3.0). Several off-stoichiometric alloys in the Ni–Mn–Sn system were also investigated: Ni0.55Mn0.20Sn0.25 (−26.6 ± 1.0); Ni0.45Mn0.30Sn0.25 (−27.5 ± 2.6); Ni0.40Mn0.35Sn0.25 (−26.6 ± 2.6); Ni0.25Mn0.50Sn0.25 (−20.9 ± 2.6); Ni0.50Mn0.30Sn0.20 (−21.0 ± 3.2); Ni0.50Mn0.35Sn0.15 (−20.1 ± 1.7). Values are compared with those from first principles calculations in published papers and the Open Quantum Materials Database (OQMD). Lattice parameters were determined using X-ray diffraction analysis. Microstructures were characterized using scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS). Differential scanning calorimetry (DSC) was used to measure the melting points of the compounds.