Structural stability of irradiated ceramics

Using the segregation-charge transfer (SCT) atomistic model, nucleation of crystalline or amorphous phases is modelled in irradiated binary oxide film s, where the bombardment conditions are suitable to the formation of dense collision cascades. Non-equilibrium compositional and electronic density pr ofiles develop at the interface between a cascade and the surrounding cryst alline matrix, as a consequence of interface enrichment of one of the film constituents. Electronic density relaxation to metastable equilibrium is tr eated schematically by local charge transfer reactions (CTR), each involvin g a pair of dissimilar atoms of the initial compound that constitute a dime r of an effective compound. The energy cost to produce an effective compoun d dimer, the difference of formation enthalpy between effective and initial compounds, and the local strain associated with a CTR are calculated for a set of 22 oxides, out of which ii are vitrified and 11 remain crystalline under ion bombardment. Qualitative differences are found in the parameter t rends between the two groups of compounds. (C) 2001 Elsevier Science B.V. A ll rights reserved.