  Using molecular dynamics simulation, we study the plastic zone created during
nanoindentation of a large CuZr glass system. The plastic zone consists of a
core region, in which virtually every atom undergoes plastic rearrangement, and
a tail, where the density distribution of the plastically active atoms decays
to zero. Compared to crystalline substrates, the plastic zone in metallic
glasses is significantly smaller than in crystals. The so-called plastic-zone
size factor, which relates the radius of the plastic zone to the contact radius
of the indenter with the substrate, assumes values around 1, while in crystals
-- depending on the crystal structure -- values of 2--3 are common. The small
plastic zone in metallic glasses is caused by the essentially homogeneous
deformation in the amorphous matrix, while in crystals heterogeneous
dislocations prevail, whose growth leads to a marked extension of the plastic
zone.
