MAEAM investigation of the structural stability and theoretical strength of Fe crystals under uniaxial loading

The structural stability and theoretical strength of BCC crystal Fe under uniaxial loading have been investigated with the modified analytic embedded‐atom method (MAEAM). Even if an orthorhombic path is applied, the deformation is spontaneous along the tetragonal path till Milstein modified Born criterion B₂₂‐B₂₃>0 is violated at λ₁=0.9064 in the compressive region. The branched orthogonal path with lower compressive stress σ₁ and energy E is preferred over the conventional tetragonal Bain path. A stress‐free FCC phase with the local maximum energy of ‐4.2186eV appearing either in compressive region (orthorhombic path) at λ₁=0.8923 or in tensile region (tetragonal path) at λ₁=1.2619 is unstable and would slip spontaneously into its near neighbor stress‐free mBCT phase with the local minimum energy of ‐4.2270eV. The initial BCC phase with the lowest energy of ‐4.280eV is the most stable in correspondence with the actual behavior of Fe. Furthermore, the stable region ranges from ‐79.7eV/nm³ to 30.6eV/nm³ in the theoretical strength or from 0.9064 to 1.1788 in the stretch λ₁ correspondingly. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)