Ground state of stoichiometric B2 FeAl

• Ground state of stoichiometric B2 FeAl has been controversial for decades.
• Energetic, mechanical, and electronic properties of FeAl are obtained.
• Lattice dynamics decides nonmagnetic ground state of FeAl.
• Electron–phonon interaction induces the negative phonon branches.

The ground state of stoichiometric B2 FeAl has been controversial for decades in the literature, and the present first principles calculation is dedicated to have a systematic study of B2 FeAl with nonmagnetic (NM), ferromagnetic (FM), antiferromagnetic (AFM), and paramagnetic (PM) states. It is found that the energetic, mechanical, and electronic properties of FeAl are not sufficient to determine the ground state, and that it is lattice dynamics which fundamentally decides the ground state of NM for FeAl. In addition, it is also revealed that the electron–phonon interaction induces the negative phonon branches of AFM and PM states, and brings about much deeper phonon dips of FM than those of NM and experiments.