Structural, elastic, phonon and electronic properties of a MnPd alloy

Abstract

The structural, elastic, phonon and electronic properties of a MnPd alloy have been investigated using the first-principles calculation. The calculated lattice constants and electronic structure agree well with the experimental results. The microscopic mechanism of the diffusionless martensitic transition from the paramagnetic B2 (PM-B2) phase to the antiferromagnetic L1 0 (AFM-L1 0) phase through the intermediate paramagnetic L1 0 (PM-L1 0) phase has been explored theoretically. The obtained negative shear modulus C′ = (C 11 - C 12)/2 of the PM-B2 phase is closely related to the instability of the cubic B2 phase with respect to the tetragonal distortions. The calculated phonon dispersions for the PM-L1 0 and AFM-L1 0 phases indicate that they are dynamically stable. However, the AFM-L1 0 phase is energetically most favorable according to the calculated total energy order, so the PM-L1 0 → AFM-L1 0 transition is caused by the magnetism rather than the electron - phonon interaction. Additionally, the AFM-L1 0 state is stabilized through the formation of a pseudo gap located at the Fermi level. The calculated results show that the CuAu-I type structure in the collinear antiferromagnetic state is dynamically and mechanically stable, thus is the low temperature phase. © 2012 Chinese Physical Society and IOP Publishing Ltd.