The modern theoretical descriptions of the stacking faults are typically based on a combination of the regular and subregular solution models with the Olson-Cohen approach [2]. This approach relies on a continuum description of the austenitic (fcc) and the martensitic (hcp) regions of the material. The input parameters entering these models are either obtained from distance measurements between the partial dislocations forming a stacking fault, or from empirical relations for the Gibbs free energy of the involved phases [3]. Although such an approach allows to estimate the stacking fault energy (SFE) it frequently provides different predictions depending on the quality of the input datasets used in the simulations. Moreover, this method is not able to resolve effects caused by the specific spatial distribution of the atoms. Thus, while providing important first insight into qualitative trends this first generation of models is not capable to study the physical mechanisms involved in the formation of stacking faults, the local arrangement and possible segregation of atoms as well as the chemical and magnetic order in the vicinity of the defect cannot be considered. Consequently, to accurately explore chemical trends and to critically asses the applicability and limits of the available phenomenological models, a full atomistic simulation of such structural defects is crucial.

The ultimate goal of the current research is the development of a generalized first principle theoretical framework that allows an accurate temperature- and composition-dependent description of the stacking fault properties in various types of steels, and the application of the method to the particular case of high-Mn steels [8]. The framework is based on density functional theory (DFT), which provides the explicit description of the chemical bonding between atoms and is an established tool for the deriving material properties. The combination of various approaches from physics of alloys, microstructure physics, physics of magnetism, thermodynamics and kinetics within a unified multiphysics framework is required due to complexity of the realistic industrially employed steels.

This project is a part of the collaborative research center "Steel - ab initio" (SFB 761) funded by Deutsche Vorschungsgemeinschaft, that aims on description of the industrially-relevant steel properties employing multiscale strategy based on the first-principles calculations.