MODELING FAST HEAVY-ION-INDUCED AMORPHIZATION IN PURE METALS

Bombardment of metallic targets with heavy, GeV energy ions results in electronic excitation beyond a threshold value of stopping power. Due to the spatial homogeneity of ion tracks, the projectile homogeneousl y deposits its energy onto all atoms within a cylinder. The radius of such an ionization cylinder is calculated, thereafter the amount of en ergy transferred to each single atom in the cylinder is evaluated: n i onization events per atoms occur, which change the atomic configuratio n from (Z) to (Z-n). Ionized atoms are ejected out of the ionization c ylinder, and they interact with matrix atoms inside a damage cylinder. Locally a starting compound [(Z) (Z-n)] is formed. Segregation at the matrix-damage cylinder interface of one component of the starting com pound gives rise to a non-equilibrium compositional profile. Relaxatio n to metastable equilibrium of the associated non-equilibrium electron ic density is simulated via charge transfer reactions, each of which i nvolves a matrix atom and an ionized atom. The reaction product is a d imer, considered a nucleus of an effective compound. The energy cost t o introduce in the matrix an effective compound dimer is calculated, t ogether with the surface properties of starting and effective compound s. Qualitative differences are found between compounds which form in m etals amorphized or, respectively crystallized under fast heavy ion ir radiation.