The Vibrational Entropy Spectra of Grain Boundary Segregation in Polycrystals
The Vibrational Entropy Spectra of Grain Boundary Segregation in Polycrystals
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DOI：
10.1016/j.actamat.2022.118630
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发表时间：
2022-12
期刊：
影响因子：
9.4
通讯作者：
Nutth Tuchinda;C. Schuh
中科院分区：
文献类型：
--
作者：
Nutth Tuchinda;C. Schuh
计算了以Pd、Pt、Ag、Au和Cu为溶质的二元Ni多晶的晶界偏析能量学的振动贡献。该问题的计算挑战是评估每个不同的晶界位置并产生位置能量和熵的全谱，这是通过多尺度方法解决的，其中全谐波计算仅在溶质原子附近完成，而基于局部谐波计算的缓冲区域影响与本体多晶体的连接。所得的偏析自由能谱说明了在不考虑振动熵的情况下，偏析温度依赖的人为性质，并强调了包括振动熵谱在内的严格计算的重要性。例如，对于5%的溶质加载水平，计算出的人工温度依赖性的大小在所探索的各种系统的总有效偏析熵的31到43%之间。最后，在多晶体中观察到位点偏析能（在谐波近似内不受振动效应的影响）与振动熵之间有很强的线性相关性，这与先前的一致位点点阵边界的工作一致；这种相关性保证了多晶中偏析计算的显著简化。
The vibrational contributions to the energetics of grain boundary segregation are calculated for binary Ni polycrystals with solutes of Pd, Pt, Ag, Au and Cu. The computational challenge of the problem is to assess each different grain boundary site and produce full spectra of both site energies and entropies, which is addressed through a multiscale approach in which a full harmonic calculation is completed only in the vicinity of the solute atom, and a buffer region based on a local harmonic calculation effects connectivity to the bulk polycrystal. The resulting segregation free energy spectra illustrate the artificial nature of segregation temperature dependencies when the vibrational entropy is not considered, and highlight the importance of including the vibrational entropy spectrum for rigorous calculations. For a 5% solute loading level, for example, the magnitude of the artificial temperature dependence calculated ranges from 31 to 43% of the total effective segregation entropy for the various systems explored. Finally, a strong linear correlation between site segregation energy (which is not much affected by vibrational effects within the harmonic approximation) and vibrational entropy is observed in polycrystals, in agreement with prior works of coincident site lattice boundaries; this correlation promises significant simplification of segregation calculations in polycrystals generally.