Experimental and computer simulation determination of the structural changes occurring through the liquid-glass transition in Cu-Zr alloys
Experimental and computer simulation determination of the structural changes occurring through the liquid-glass transition in Cu-Zr alloys
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DOI：
10.1080/14786435.2010.494585
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发表时间：
2010-01-01
影响因子：
1.6
通讯作者：
Rogers, J. R.
中科院分区：
文献类型：
--
作者：
Mendelev, M. I.;Kramer, M. J.;Rogers, J. R.
采用分子动力学（MD）模拟了Cu-Zr合金液态玻璃化转变过程中发生的结构变化。总散射函数（TSF）及其相关的主要漫散射峰位置（Kp），高度（Kh）和半峰全宽（KFWHM）被用作度量，以比较模拟与高能X射线散射数据。模型和实验的TSF之间的差异的残差是0.03的液体和约0.07的玻璃。在研究的组成范围内，Zr 1-xCux（0.1 × 0.9），Kp，Kh和KFWHM显示出强烈的依赖于组成和温度。模拟和实验数据之间的相互关联很好。分子动力学模拟结果表明，在冷却过程中，Cu-Zr键的变化最大，而Cu-Cu键的变化最小。在第二层和第三层中，部分对相关性的变化更容易看到。玻璃中的Voronoi多面体（VP）仅由几种成分依赖的选择类型主导。在深过冷液体中，占主导地位的VP的相对浓度以其相对比例迅速变化。实验确定的最佳玻璃成形性的区域，xCu 65%，显示出最大的温度依赖性的变化，在MD模拟的深度过冷液体。该区域的扩散率和系统的总能量也表现出非常强的温度依赖性。这些数据指向一个强大的拓扑结构的变化，在最好的玻璃形成合金和并发的变化，在深过冷液体中的VP化学。
Molecular dynamics (MD) simulations were performed of the structural changes occurring through the liquid-glass transition in Cu-Zr alloys. The total scattering functions (TSF), and their associated primary diffuse scattering peak positions (Kp), heights (Kh) and full-widths at half maximum (KFWHM) were used as metrics to compare the simulations to high-energy X-ray scattering data. The residuals of difference between the model and experimental TSFs are 0.03 for the liquids and about 0.07 for the glasses. Over the compositional range studied, Zr1-xCux (0.1 x 0.9), Kp, Kh and KFWHM show a strong dependence on composition and temperature. The simulation and experimental data correlate well between each other. MD simulation revealed that the Cu-Zr bonds undergo the largest changes during cooling of the liquid, whereas the Cu-Cu bonds change the least. Changes in the partial-pair correlations are more readily seen in the second and third shells. The Voronoi polyhedra (VP) in glasses are dominated by only a few select types that are compositionally dependent. The relative concentrations of the dominant VPs rapidly change in their relative proportion in the deeply undercooled liquid. The experimentally determined region of best glass formability, xCu 65%, shows the largest temperature dependent changes for the deeply undercooled liquid in the MD simulation. This region also exhibits very strong temperature dependence for the diffusivity and the total energy of the system. These data point to a strong topological change in the best glass-forming alloys and a concurrent change in the VP chemistry in the deeply undercooled liquid.