Electronic and Vibrational Properties of Fe₂NiAl and Co₂NiAl Full Heusler Alloys: A First-Principles Comparison.

We provide a comparative first-principles investigation of the structural, electronic, vibrational, and thermodynamic properties of the full Heusler compounds, cubic Fe2NiAl, and tetragonally distorted Co2NiAl. In both cases, we find the inverse Heusler structure to be in close competition with a layered arrangement of the elements, which breaks cubic symmetry and is accompanied by significant absolute values for the magnetocrystalline anisotropy energy. While for Fe2NiAl the layered arrangement is predicted as a new ground state, we show evidence that it might become dynamically stable around room temperatures also for Co2NiAl. We identify in both systems subtle differences in the electronic and vibrational density of states between the different structures, which might be related to their particular stability. [ABSTRACT FROM AUTHOR]