Small clusters of vacancies and helium in molybdenum

Formation, binding, and configuration change energies of di- and trivacancies with and without atoms have been computed for molybdenum, a programme being used that simulates the relaxation of a lattice around defects. An approximate rule is given for calculating similar energies of larger clusters from mono- and divacancy data. This rule may be used in computer simulation studies of defect annealing in irradiated molybdenum. The effect of helium on the stability and mobility of V2, V3, and V4 vacancies and models for growth to larger clusters is discussed.