One of the outstanding questions in radiation damage is how stacking-fault
tetrahedra (SFTs) can be formed below the vacancy migration temperature. Us
ing molecular dynamics simulations of energetic collision cascades, we now
describe how a stacking-fault tetrahedron can be created directly in a coll
ision cascade. We also show that, while the number of SFTs is small at low
temperatures, at elevated temperatures the number will increase by rearrang
ement of complex damage clusters into the SFTs, in good agreement with expe
riments. (C) 1999 American Institute of Physics. [S0003-6951(99)04918-9].