MIGRATION OF SMALL INTERSTITIALS CLUSTERS IN BCC METALS: A MODEL FOR MOLYBDENUM

R. C. PASIANOT Y V. P. RAMUNNI

Buenos Aires, Argentina

Congreso; SAM/CONAMET 2009; 2009

Depto Materiales CAC/CNEA y UNSAM

The migration mechanisms of small self­interstitial clusters in bcc Molybdenum are studied by computer  simulation. This is a continuation of our previous work (Ramunni and Pasianot, SAM 2007) where only the  single interstitial was considered; here, the sizes up to four units being tackled, assure correct extrapolation  of the general trends.  The research is pertinent to the post­collapse cascade stages of radiation damage,  when defects diffuse to sinks and agglomerate into bigger units. Two interaction models are considered, one  rather standard many­body central forces potential, and another one including angle contributions to the  energy, which in principle is a more consistent representation of a bcc transition metal. Also, two techniques  are employed: Molecular Dynamics and Monomer. The former provides global parameters of the diffusion process;   the   latter   is   a   static   technique   to   search   the   potential   energy   surface   for   saddle   points,   thus  providing detailed information on transition events. Reasonable agreement is found among the two, though  the connection between the static parameters with the dynamic ones may not be straightforward. The extent  to which the interaction model affects the diffusion parameters turns out to be cluster dependent. Notably, in  some   cases  where   such  an influence  is  small,  the  underlying  microscopic  mechanisms  are  nevertheless  different.