Helium bubbles impact mechanical properties of nuclear materials. An Fe-Ni-Cr-H-He potential has been developed to enable molecular dynamics simulations of helium bubble nucleation and growth. This is accomplished by addressing three challenging paradoxes: (a) helium forms tightly bound dimers and clusters in the lattice but are only bound by weak van de Waals forces in the gas phase, (b) helium diffuses readily in metals yet significantly distort the lattice causing large volume expansions; (c) helium prefers tetrahedral interstitial sites to the larger octahedral sites despite strong repulsion from metal atoms. Our potential reproduces quantum mechanical results on relevant properties to bubble nucleation and growth. In addition to validation by static properties, molecular dynamics simulations establish that our potential enables the nucleation of helium bubbles from an initial random distribution of He interstitial atoms while at the same time capturing the equation of state in the pure He phase.
Acknowledgement- SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.