The structure of small Ta clusters

The structure of small tantalum clusters is investigated by using molecular dynamics simulations. A structural evolution from polytetrahedral structures to layered Frank–Kasper-type structures is revealed as cluster size increases to N∼100 atoms. The lowest-energy structures have been located for clusters with N≤78. The bulk-like (bcc) structure becomes the most stable structure beyond N∼100. The stabilized structure strongly depends on the cooling rate. A structure similar to β-Ta, a σ-type Frank–Kasper structure, can be obtained by rapid cooling. The structural properties of small Ta clusters presented in the paper provide insight into the formation and origin of β-phase Ta. The growth of β-Ta films in practice may be due to the nucleation of Ta clusters with layered Frank–Kasper-type structure during the initial stage of film growth.