【International Papers】Large-scale atomistic study of plasticity in amorphous gallium oxide with ab-initio accuracy

      Researchers from the Tampere University have published a dissertation titled "Large-scale atomistic study of plasticity in amorphous gallium oxide with ab-initio accuracy" in scientific reports.

Acknowledgements

      We acknowledge funding from the Research Council of Finland project numbers 360436, 315451, 315453, 326426, 338750 and 332347. J. Zhao acknowledges the National Natural Science Foundation of China under Grant 62304097; Guangdong Basic and Applied Basic Research Foundation under Grant 2023A1515012048; Shenzhen Fundamental Research Program under Grant JCYJ20230807093609019. J. Byggmästar acknowledges funding from the Research Council of Finland Flagship programme: Finnish Center for Artificial Intelligence (FCAI). The computational resources granted by the CSC - IT Center for Science projects 2003839 (LAPLAS Glass Plasticity at Room Temperature) and hy3898, Finland, and by the Finnish Grid and Cloud Infrastructure project (FGCI; urn:nbn:fi:research-infras-2016072533) are gratefully acknowledged.

Abstract

      Compared to the widely investigated crystalline polymorphs of gallium oxide (Ga₂O₃), knowledge about its amorphous state is very limited. With the help of a machine-learning interatomic potential, we conducted large-scale atomistic simulations to investigate the formation and plastic behavior of amorphous Ga₂O₃ (a-Ga₂O₃). Amorphization of gallium oxide melt is successfully observed at ultrahigh cooling rates, including a distinct glass transition. The glass transition temperature is evaluated to range from 1234 to 1348 K at different cooling rates. Structural analysis shows similarities between a-Ga₂O₃ and amorphous alumina (a-Al₂O₃) in many aspects, including pair distribution function, coordination distribution, and bond angle distribution. In the tension simulations, highly plastic behavior at room temperature is observed, highly comparable to a-Al₂O₃. Based on multiple quantitative characterization results, we show that a-Ga₂O₃ exhibits a higher nucleation rate of localized plastic strain events compared to a-Al₂O₃, which can increase the material’s resistance to shear banding formation during deformation.

Conclusions

      In summary, we investigated the room temperature plasticity of a-Ga₂O₃ with large-scale atomistic simulations based on a newly developed ML-IAP, tabGAP. Results are compared with existing experimental and computational results. On an atomistic simulation time scale, the IAP can produce an a-Ga₂O₃ structure that has density and structural properties comparable to the reported properties of the material. Therefore, the new tabGAP IAP is efficient and reliable in modeling a-Ga₂O₃. Computational results validate that following a melt-quenching preparation process, a glass transition occurs in Ga₂O₃.

      Tensile test simulation shows that overall a-Ga₂O₃ exhibits room temperature plasticity comparable to that earlier observed in a-Al₂O₃ with similar number of atoms momentarily exhibiting a high local plasticity. However, differences were also found. When deformed at the same strain rate, the two materials have different fractions of atoms in the LPSE clusters that mediate the plasticity. This indicates a higher LPSE nucleation rate for a-Ga₂O₃ which can increase the resistance of the material to shear banding, which is a known failure mechanism in amorphous materials. The results of this work show that the ML-IAP is a useful tool in the study of the mechanical properties of amorphous materials, providing predictive information for experimental study.