The stability of the β-phase of tantalum: A molecular dynamics study

Molecular dynamics simulations have been performed on tantalum clusters using the embedded-atom-method potential. Melting simulations show that β-Ta. clusters have a lower melting temperature than the same size clusters of α-Ta (bec structure). Pure β-Ta clusters are quite stable and do not transform to the α-Ta on melting. Simulations on Ta clusters with mixed α- and β-phases reveal that inclusion of a bcc-Ta cluster within a β-Ta cluster induces the β-to-α-phase transformation at a temperature far below the melting point of a pure β-Ta cluster, depending on the cluster size and α-to-β-atom ratio. The results suggest that the observed phase transformation of β-Ta thin films is due to the presence of α-phase inclusions in the β-Ta film grains.