СRYSTALLOGEOMETRY OF FILLING COORDINATION SPHERES IN NANOPARTICLES OF AN ALLOY OF COMPOSITION A3B FORMING THE D03 SUPERSTRUCTURE

10.25712/ASTU.1811-1416.2024.03.011

Abstract

In the crystal structure of high-entropy multicomponent alloys, nanoparticles of intermetallic compounds and ordering alloys are observed as constituent components. Among the possible intermetallic phases based on the bcc lattice, four types of superstructures can be distinguished: B2 (composition AB), B32 (composition AB), D0₃ (composition A₃B) and C11_b (composition A₂B, tetragonal packing). In this work, we propose a simple method for packing nuclei of the intermetallic phase of the D0₃ superstructure, which are formed in the first 21 coordination spheres. The technique makes it possible to construct the ideal crystal geometry of superstructure nuclei in a sequence of coordination spheres. It is obvious that in reality, especially at very small sizes, the ideal packing turns out to be unstable, and during the transition to equilibrium, packings with non-crystalline symmetry axes of the fifth and seventh order will appear. However, the proposed procedure makes it possible to construct the ideal crystal geometry of superstructure nuclei. The actual configuration of nanoparticles can be achieved by connecting a subsequent material relaxation procedure using molecular dynamics methods. The work uses the idea of seven regular polyhedra: cube, cuboctahedron, truncated cube, truncated cuboctahedron, rhombicuboctahedron, octahedron, truncated octahedron.