It has recently become clear that electron irradiation can recrystallize am
orphous zones in semiconductors even at very low temperatures and even when
the electron beam energy is so low that it cannot induce atomic displaceme
nts by ballistic collisions. We study the mechanism of this effect using cl
assical molecular dynamics augmented with models describing the breaking of
covalent bonds induced by electronic excitations. We show that the bond br
eaking allows a geometric rearrangement at the crystal-amorphous interface
which can induce recrystallization in silicon without any thermal activatio
n.