**5. Conclusions**

In summary, He effects on generation and growth of cracks in nanocrystalline BCC-Fe are studied in the present work. The modification of microstructure caused by the He distributed in the nanocrystalline is analyzed by the change of simulated XRD patterns and the atomic volume. For the nanocrystalline BCC Fe with the average grain size of 8.28 ± 0.32 nm, the following conclusions are obtained:


**Author Contributions:** Conceptualization, C.X.; Investigation, C.X. and W.W.; Methodology, C.X. and W.W.; Software, C.X. and W.W.; Visualization, C.X.; Writing—original draft, C.X.; Writing—review and editing, C.X. and W.W.

**Funding:** This research received no external funding.

**Acknowledgments:** This work was supported by laboratory of computation science at Yantai University.

**Conflicts of Interest:** The authors declare no conflict of interest.
