Replacement Collision Sequences

In Sect. 7.2 the concept of a replacement collision was introduced. A replacement collision was possible if a PKA had sufficient energy to displace an atom from its lattice site but was left with energy less than Ed and fell into the vacated site it just created. Early computer simulations of the irradiation process showed that the number of such replacement events greatly exceeded the number of permanent displacements left in the lattice. While such events have little influence on monatomic materials, replacement collisions can produce considerable disorder in ordered polyatomic materials. 

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As mentioned above. Vineyard s group at Brokhaven was the first one to use computer simulations for radiation damage studies [3]. Their simulations showed that Frenkel pairs are produced in metals as a result of replacement collision sequences (RCS), where one atom replaces its neighbor in a chain of events that results in a separation of a few atomic distances between the vacant site and the interstitial atom. 

RCS replacement-collision sequence SSAR solid-state amorphizing reaction... 

Figure 12. Unit cell of ordered Ni,Mn and (1 00) Ni-Mn planes before and after occurrence of a replacement collision sequence RCS (From Kirk et at., 1977)...

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