Thermodynamics of mixing in an isostructural solid solution: Simulation methodologies and application to the rutile-cassiterite system
Thermodynamics of mixing in an isostructural solid solution: Simulation methodologies and application to the rutile-cassiterite system
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DOI：
10.2138/am-2016-5490
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发表时间：
2016-05
影响因子：
3.1
通讯作者：
Xin Liu;V. Vinograd;Xiancai Lu;E. V. Leonenko;N. Eremin;Rucheng Wang;B. Winkler
中科院分区：
文献类型：
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作者：
Xin Liu;V. Vinograd;Xiancai Lu;E. V. Leonenko;N. Eremin;Rucheng Wang;B. Winkler
摘要以金红石-锡石固溶体为例，探讨了两种不同方法模拟固溶体热力学混合性质的准确性。这两种方法都采用了构型焓在成对相互作用能量方面的展开。在第一种方法中，配分函数直接从2 × 2 × 4超级单体内所有Ti/Sn构型的多余能量计算。在第二种方法中，混合自由能是用蒙特卡罗法计算的热平均焓的热力学积分来计算的，使用8 × 12 × 16超级单体。通过蒙特卡罗模拟得到的相关系与现有的实验数据吻合较好，但对自由能进行了修正，以消除多余振动熵的影响。配分函数的直接计算只有在将构型熵修正为与高温极限下的理想混合相一致时才能提供合理的相关系。讨论了这两种方法的优缺点。研究结果一般适用于等结构固溶体模型。
Abstract The accuracies of two different approaches to model thermodynamic mixing properties of solid solutions are explored using the rutile-cassiterite solid solution as an example. Both methods employ an expansion of the configurational enthalpy in terms of pairwise interactions energies. In the first method the partition function is directly computed from the excess energies of all Ti/Sn configurations within a 2 × 2 × 4 supercell. In the second method the free energy of mixing is calculated by a thermodynamic integration of the thermally averaged enthalpies computed with the Monte Carlo method using an 8 × 12 × 16 supercell. The phase relations derived from Monte Carlo simulations agree well with the available experimental data, under the condition that the free energy is corrected for the effect of the excess vibrational entropy. The direct calculation of the partition function provides reasonable phase relations only when the configurational entropy is corrected to be consistent with the ideal mixing in the high-temperature limit. Advantages and drawbacks of the both approaches are discussed. The findings are generally applicable to models of isostructural solid solutions.