Classifying Intermetallic Tetragonal Phase of All-d-Metal Heusler Alloys for Catalysis Applications

Heusler alloy is an intermetallic alloy that is applied in various applications due to its combinatorial tunability in high throughput screening. Recently, this intermetallic structure has also emerged as a potential candidate for heterogeneous catalysis applications. While Heusler compounds can exist in two crystal phases, cubic and tetragonal, it has been observed that the catalytic activity is enhanced in the tetragonal phase for several catalysis reactions due to the ordering effect and symmetry breaking, prompting a need to understand the factors responsible for the preferred phase of Heusler alloys. In this work, we use simple descriptors, namely, spin moment and occupancy of d-electrons, to predict the stable (tetragonal vs. cubic) phase of all-d-metal Heusler alloys. The classification accuracy of the proposed descriptors using a support vector machine is shown to be 86%. We further find that 66% of the all-d-metal Heusler alloys have scaling relations between the d-electron occupancy and spin moments due to a pseudogap, which would allow the evaluation of the descriptors without costly density functional calculations. We expect that the present phase classification model can potentially reduce the computational cost for the high throughput screening of Heusler compounds in various catalysis applications.