Structure and stability of the stoichiometric al3 fe phase

Abstract

A disordered stoichiometric Al3 Fe phase was obtained when synthesizing Al8 Fe3 by the spark plasma sintering (SPS) approach and its crystal structure was determined by the single-crystal X-ray diffraction (SXRD) techniques. The refined structure is an isotype of the reported Al5 Fe2 phase, only different in the site occupation factors (s. o. f.) of Al2 and Al3 atoms, which was refined to be 0.431 (13) and 0.569 (13), respectively. Stimulated by the structural refinement results, an ordered stoichiometric Al3 Fe phase was established. First-principles calculations reveal that the ordered Al3 Fe phase is mechanically and dynamically stable and has a much lower value of enthalpy of formation than any other proposed Al3 Fe phases, although it is also metallic and metastable.