Total and net displacement functions for polyatomic materials

• Published in: Journal of nuclear materials 1981-01, Vol.101 (3), p.261-276
• Main Authors: Parkin, Don M., Coulter, C.Alton
• Format: Article
• Language: English
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/0022-3115(81)90169-0

Using a continuous-slowing-down, random amorphous material model in which displacement and recombination processes are determined by sharp displacement thresholds and capture energies, we have studied displacement cascades in a number of diatomic materials and a few triatomic materials. The results obtained are presented here in terms of a set of displacement efficiencies for each material which correlate the calculated number of net displacements with the damage energies, displacement thresholds, and stoichiometry of the material. Materials for which the ratio of heavy to light mass is less than about four (Type 1) show somewhat different displacement cascade characteristics than those for which the mass ratio is greater than four (Type 2). In addition, for each material the dependence of the cascades on the energy of the primary has different properties in two different energy ranges. In Region I, extending from the lowest displacement threshold to about I keV for Type-1 materials and to about 100 keV for Type-2 materials, the displacement efficiencies show strong dependence on energy and on the atom type of the primary. In Region 2 (energies higher than Region 1) the displacement efficiencies are nearly independent of energy and of the type of the primary. Cascades in Type-1 materials can show strong dependence on the capture probability for atoms on sites of unlike type; this dependence is discussed, as is the dependence of cascade structure on displacement threshold. Rather strong nonstoichiometric behavior is demonstrated for certain Type-2 materials. Comparisons are made with a few previous calculations for diatomic materials.