  We study order transitions and defect formation in a model high-entropy alloy
(CuNiCoFe) under ion irradiation by means of molecular dynamics simulations.
Using a hybrid Monte-Carlo/molecular dynamics scheme a model alloy is generated
which is thermodynamically stabilized by configurational entropy at elevated
temperatures, but partly decomposes at lower temperatures by copper
precipation. Both the high-entropy and the multiphase sample are then subjected
to simulated particle irradiation. The damage accumulation is analyzed and
compared to an elemental Ni reference system. The results reveal that the
high-entropy alloy---independent of the initial configuration---installs a
certain fraction of short-range order even under particle irradiation.
Moreover, the results provide evidence that defect accumulation is reduced in
the high-entropy alloy. This is because the reduced mobility of point defects
leads to a steady state of defect creation and annihilation. The lattice
defects generated by irradiation are shown to act as sinks for Cu segregation.
