Dai X D, Li J H, Liu B X
Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
J Phys Chem B. 2005 Mar 17;109(10):4717-25. doi: 10.1021/jp0453461.
With the aid of ab initio calculations, an n-body potential of the Ni-Nb system is constructed under the Finnis-Sinclair formalism and the constructed potential is capable of not only reproducing some static physical properties but also revealing the atomistic mechanism of crystal-to-amorphous transition and associated kinetics. With application of the constructed potential, molecular dynamics simulations using the solid solution models reveal that the physical origin of crystal-to-amorphous transition is the crystalline lattice collapsing while the solute atoms are exceeding the critical solid solubilities, which are determined to be 19 atom % Ni and 13 atom % Nb for the Nb- and Ni-based solid solutions, respectively. It follows that an intrinsic glass-forming ability of the Ni-Nb system is within 19-87 atom % Ni, which matches well with that observed in ion beam mixing/solid-state reaction experiments. Simulations using the Nb/Ni/Nb (Ni/Nb/Ni) sandwich models indicate that the amorphous layer at the interfaces grows in a layer-by-layer mode and that, upon dissolving solute atoms, the Ni lattice approaches and exceeds its critical solid solubility faster than the Nb lattice, revealing an asymmetric behavior in growth kinetics. Moreover, an energy diagram is obtained by computing the energetic sequence of the Ni(x)Nb(100)(-)(x) alloy in fcc, bcc, and amorphous structures, respectively, over the entire composition range, and the diagram could serve as a guide for predicting the metastable alloy formation in the Ni-Nb system.
借助从头算计算，在芬尼斯 - 辛克莱形式体系下构建了Ni - Nb体系的n体势，所构建的势不仅能够再现一些静态物理性质，还能揭示晶体到非晶转变的原子机制及相关动力学。应用所构建的势，使用固溶体模型进行的分子动力学模拟表明，晶体到非晶转变的物理起源是晶格在溶质原子超过临界固溶度时崩塌，对于Nb基和Ni基固溶体，临界固溶度分别确定为19原子%的Ni和13原子%的Nb。由此可知，Ni - Nb体系的本征玻璃形成能力在19 - 87原子%的Ni范围内，这与离子束混合/固态反应实验中观察到的结果非常吻合。使用Nb/Ni/Nb（Ni/Nb/Ni）三明治模型的模拟表明，界面处的非晶层以逐层模式生长，并且在溶解溶质原子时，Ni晶格比Nb晶格更快地接近并超过其临界固溶度，揭示了生长动力学中的不对称行为。此外，通过分别计算Ni(x)Nb(100)( - )(x)合金在整个成分范围内fcc、bcc和非晶结构的能量序列，获得了一个能量图，该图可作为预测Ni - Nb体系中亚稳合金形成的指南。
