Shed light on new growth pattern in rapid solidified Ta metal: MD simulation, DFT calculation and CALYPSO search

Abstract

Aiming at the micro-structures of rapid solidified Ta system under cooling rate of 1×1010 K/s, the lowest-energy and meta-stable geometric structure of Tan (n = 19–30) clusters are systematically investigated via MD simulation, DFT calculation and CALYPSO search. It is revealed that the ground-state geometric structure of free Ta clusters plays a significant role in determining its solidified atomic structures and evolution laws in the early stage of nucleation. We explained why the hexagonal close packed (hcp) atomic clusters (Ta22) dominate the solid state of Ta when cooled at a rate of 1 × 1010 K/s. And found that the coexistence of slightly distorted icosahedral (Ta13) and hcp clusters (Ta22) at 300 K is due to the high energy stability of free Ta26–C2v (B) cluster. The larger size of Ta clusters with a perfect closed-shell geometric structure plays a key role in energetic effects, as demonstrated by their thermodynamic stability in terms of binding energy. Additionally, electronic structure stability is achieved when there are fewer electrons on the Fermi level (N(EF)), resulting in Ta atomic clusters that exhibit higher energetic stability and lower chemical activity. Our analysis of the interaction between different atoms in Ta clusters revealed that stronger electronic interactions of central(c)-central(c) and central(c)-shell(s) atoms contribute to the higher energy and chemical stability. Finally, we provide insights into understanding the growth patterns of nucleation in liquid metals through an examination of geometric and electronic structures of free Ta cluster.