Free-energy based pair-additive potentials for bulk Ni-Al systems: application to study Ni-Al reactive alloying.
Free-energy based pair-additive potentials for bulk Ni-Al systems: application to study Ni-Al reactive alloying.
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DOI：
10.1063/1.4747546
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发表时间：
2012-09
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通讯作者：
S. Izvekov;B. Rice
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文献类型：
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作者：
S. Izvekov;B. Rice
我们使用Born-Oppenheimer方法通过力匹配（FM）离子力和单相（体积液体）从头算分子动力学（MD）模拟的病毒数据，提出了新的数值对加性Al， Ni和Al-Ni势。势由分段函数（样条）表示，因此，不局限于特定的解析函数形式选择。具有维里约束的调频法自然地产生了一个势，它描绘了参考系综的离子自由能面。为了进一步提高调频系综的自由能能，对调频过程进行了修改，使电位偏置，以重现参考相（FCC-Al, FCC-Ni, B2-NiAl）的实验熔化温度，这是拟合集中唯一的宏观数据。然后对合成势在模拟大块金属相中的性能进行了评价。应用该模型对温度为1300 K、温度为P = 0 ~ 5 GPa的Ni-Al双分子层自扩散放热反应进行了MD模拟。与实验观察相一致，新模型真实地描述了整个反应过程中一系列的包晶相变，并以真实的速率进行。反应通过Al和Ni原子在界面处的层间扩散进行，并在Al熔体中形成B2-NiAl。在过去，这种物质反应已被证明很难用当时存在的电位来观察。
We present new numerical pair-additive Al, Ni, and Al-Ni potentials by force-matching (FM) ionic force and virial data from single (bulk liquid) phase ab initio molecular dynamics (MD) simulations using the Born-Oppenheimer method. The potentials are represented by piece-wise functions (splines) and, therefore, are not constrained to a particular choice of analytical functional form. The FM method with virial constraint naturally yields a potential which maps out the ionic free-energy surface of the reference ensemble. To further improve the free energetics of the FM ensemble, the FM procedure is modified to bias the potentials to reproduce the experimental melting temperatures of the reference (FCC-Al, FCC-Ni, B2-NiAl) phases, the only macroscopic data included in the fitting set. The performance of the resultant potentials in simulating bulk metallic phases is then evaluated. The new model is applied to perform MD simulations of self-propagating exothermic reaction in Ni-Al bilayers at P = 0-5 GPa initiated at T = 1300 K. Consistent with experimental observations, the new model describes realistically a sequence of peritectic phase transformations throughout the reaction and at a realistic rate. The reaction proceeds through interlayer diffusion of Al and Ni atoms at the interface with formation of B2-NiAl in the Al melt. Such material responses have, in the past, been proven to be difficult to observe with then-existing potentials.