Six new transformation pathways connecting simple crystal structures and common intermetallic crystal structures

Continuous pathways that connect different crystal structures can play a crucial role in determining the mechanisms with which structural phase transformations occur. The number of known pathways connecting metallic phases, such as the Bain path and the Burgers path, are limited. Here we discover six new pathways that connect the BCC, FCC, HCP and ω crystal structures to more complex intermetallic compound crystal structures. High throughput first-principles calculations of over 600 metallic binary AnBm compounds having compositions n:m of 1:1, 2:1 and 3:1 show that the newly discovered pathways can be initiated as a result of dynamical instabilities in the precursor phase. The pathways are initiated by specific precursor orderings of A and B atoms over the sites of the simpler parent crystal structures. We find that a large difference in the atomic radii between the constituents of the alloy is a common trigger of these instabilities. The results of this study have important implications for solid-state nucleation mechanisms of intermetallic compounds and suggest systematic approaches with which new intermetallic crystal structures can be discovered, especially in high dimensional composition spaces.