Molecular dynamics simulation of the solid-liquid interface migration in terbium

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Mendelev, Mikhail
Zhang, Feng
Song, H.
Sun, Yang
Wang, Cai-Zhuang
Ho, Kai-Ming
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Ames National Laboratory

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We developed a Tb embedded atom method potential which properly reproduces the liquid structure obtained from the ab initio molecular dynamics simulation, the hexagonal close packed (hcp)-body-centered cubic (bcc) phase transformation, and melting temperatures. At least three crystal phases [hcp, face-centered cubic (fcc), and bcc] described by this potential can coexist with the liquid phase. Thus, the developed potential provides an excellent test bed for studies of the completive phase nucleation and growth in a single component system. The molecular dynamics simulation showed that all crystal phases can grow from the liquid phase close to their melting temperatures. However, in the cases of the hcp and fcc growth from the liquid phase at very large supercoolings, the bcc phase forms at the solid-liquid interface in the close packed orientations in spite of the fact that both hcp and fcc phases are more stable than the bcc phase at these temperatures. This bcc phase closes the hcp and fcc phase from the liquid such that the remaining liquid solidifies into the bcc phase. The initial hcp phase then slowly continues growing in expense of the bcc phase.