Ab initio-based mean-field theory of the site occupation in the Fe-Crσ-phase

Ab Initio Study of Lattice Site Occupancies in Binary Sigma Phases Using a Single-Site Mean Field Model

“…As has been shown in [14], the contribution from local lattice relaxations to the formation enthalpy is about 2.5 mRy / 30 at. cell in the FeCr case, which was expected due to small size mismatch of Fe and Cr.…”

“…Furthermore, as has already been discussed in our previous works [14,16], longitudinal spin fluctuations should exist at high temperature. These are thermal Stoner-like many-body excitations which lead to fluctuations of the magnitude of the local magnetic moments.…”

“…In order to find the atomic occupancies of the σ-phase sublattices, we minimize the Helmholtz free energy F , which can be written in the following form for a given composition and temperature [14][15][16]:…”

“…However, most of these methods were based on a formalism, which is quite computationally demanding. Alternatively, we have recently proposed a simpler approach to calculate the site preference in the binary σ-phases [14][15][16]. It is based on a simple single-site mean-field model, which recently has demonstrated to be able to produce quite accurate results for the site occupancy of Fe and Cr in the Fe-Cr σ-phase.…”

Non-Stoichiometry and Calphad Modeling of Frank-Kasper Phases

“…Instead of using BWA-CEF, Cieslak et al [43] used a combined KKR-CPA method for modeling the chemical disorder. Finally, a new calculation has been done by using Ising-type configurational Hamiltonian and a single-site mean-field approach for two different σ-Cr-Fe compositions [44]. Figure 6.…”