**5. Conclusions**

We observed that early stage nanoscale delamination at a particle-matrix interface was a three-stage process: (1) a nuclei of excess free volume is formed at the particle-matrix interface, either immediately upon loading or after a brief delay; (2) subsequently, the nuclei grows in the absence of dislocation activity in a process we term *lattice-trapped delamination*; (3) when the crack reaches sufficient size and the crack tip stress intensity is sufficient, Shockley partial dislocations are emitted causing a rapid acceleration of crack growth and ultimately complete debonding of the particle-matrix interface. The second stage, lattice-trapped delamination, as described for the first time herein, limits the rate of early-stage growth of the nanocrack, and is not only relevant to shock spallation, but extrapolation of the kinetics of this process suggest that it is also relevant at quasi-static strain rates for micrometer-scale particles.

**Author Contributions:** Conceptualization, R.B.S.; methodology, R.B.S. and Q.Q.Z.; analysis, R.B.S., Q.Q.Z., and B.L.B.; writing, R.B.S., Q.Q.Z., and B.L.B. All authors have read and agreed to the published version of the manuscript.

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

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are openly available through Zenodo at 10.5281/zenodo.4420413.

**Acknowledgments:** B.L.B. was supported by the Center for Integrated Nanotechnologies funded by the DOE Office of Basic Energy Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. The views expressed in the article do not necessarily represent the views of the U.S. DOE or the United States Government.

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