The movies in Supplementary Materials of “An operational window for radiation-resistant materials based on sequentially healing grain interiors and boundaries”by Xiangyan Li et al.

Movie S1: MD simulation of a collision cascade induced by a 3 keV PKA located about 23 Å on one side of the GB over a time of 4012 ps at 1000 K for a symmetric tilt GB Σ5(310)/[001] in bcc Fe (Part a: Defect evolution within grain interiors; Part b: Defect evolution within the GB). Some of the typical snapshots in this movie are shown in Fig. 1. Atoms are colored with their potential energies and those with energy deviation from the bulk value less than 0.1 eV are treated as non-defective and are not shown; a vacancy is characterized as a 14-atom cluster consisting of its first and second nearest neighbors. And the cluster comprises less than 14 atoms within the GB where the coordination number is smaller than that in the bulk. In the movie, the time is also given indicating time scales of different events. Evidently, the movie can be divided into several stages according to the variation of defect numbers and their spatial locations in the grain interior or within the GB. At the initial stage from 0.0 to 0.5 ps, the cascade volume sharply increases followed by a fast shrink because of the defect recombination from 0.5 to 12 ps. Then only two vacancies are left near the GB which also disappear up to 267 ps when the system heals its region in the grain interior. Another important stage from 0 to 4012 ps is the healing of the damaged GB, which surprisingly takes much longer time compared with previous stages.

Movie S2: The annihilation of one vacancy located at a site about 4.5 Å perpendicular to the GB and an interstitial trapped within the GB. Here V represents a vacancy and the red line marks the GB position. The crystal directions X and Y are the same as those in Fig. 1. And the atoms with displacements smaller 0.6 Å are not shown. The movie clearly shows concerted motion of three atoms in the annihilation. Furthermore, the nearest neighbor of the vacancy also has displacements at an early stage suggesting that the vacancy is not immobile during the annihilation near the GB.

Movie S3: The annihilation of one vacancy and an interstitial within the GB. Here symbols are defined as in Movie S2. And we only display the atoms with displacements larger 0.6 Å. The movie demonstrates that the annihilation within the GB also involves concerted motion of multiple atoms similar to the recombination near the GB (Movie S2).

Movie S4: The diffusion of interstitials within the GB. The migration path is determined using the TAD method and the transition has a barrier of 0.59 eV (Fig. S20b) involving collective motion of three atoms with displacements larger 0.6 Å. Here Y and Z are the same as in Fig. 1. Thus the detected easy path is parallel to the tilt axis Z.