From Fe-, Ni-, Co-based Heusler Alloys to High Entropy Alloys: The Role of p-d Hybridization and Positional Disorder in Structural Transformations

• Applicant: Dr. Olga Miroshkina
• Subject Area: Computer-Aided Design of Materials and Simulation of Materials Behaviour from Atomic to Microscopic Scale ; Theoretical Condensed Matter Physics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 539118894

With the increasing energy demand and environmental concerns, the new functional materials with magnetostructural phase transition become essential. These materials can demonstrate soft and hard magnetic properties, magnetocaloric, and shape memory effects. To be used widely, smart functional materials should be ecologically friendly and consist of low-cost abundant elements. Thus, searching for such materials is the topmost challenge for the materials scientist. The proposed project aims to find new materials with structural phase transition suitable for functional application with the help of density functional theory, Monte Carlo simulations, and machine learning force fields among complex Heusler and high-entropy alloys (HEAs). To control and tune the physical and functional properties of complex magnetic materials, it is important to investigate their electronic structure. In this project, the special focus will be made on the p-d covalent hybridization and revealing the mechanisms responsible for the structural transformations in HEAs. For this, it would be interesting to compare the electronic structure and exchange interactions with that of Heusler alloys, which are (partially) ordered. This will allow to distinguish the role of the disorder in the structural transitions in complex magnetic materials. The objective is to understand why the transformation to the hcp phase is possible in HEAs, while transition to the hexagonal phase is not observed for Heusler alloys. To make a step in this direction, the electronic, magnetic, and structural properties will be theoretically investigated at the nano-scale for complex multicomponent compounds starting from the ordered Fe-, Ni-, Co-based Heusler alloys via introducing the disorder in these systems and ending with the five-component HEAs consisting of the same elements. The main goal of this project is to understand the potential competition between Bain (bcc ->fcc) and Burgers (bcc ->hcp) paths in multicomponent magnetic Heusler-based alloys depending on the valence electron concentration and crystal ordering. As a result of project implementation, the complex multicomponent magnetic materials based on Fe, Ni, and Co that demonstrating structural phase transitions between fcc, bcc, hcp phases with high magnetization and Curie temperature will be predicted.

• DFG Programme: Research Grants