Designing Nanostructures for Interfacial Phonon Transport via Bayesian Optimization
Designing Nanostructures for Interfacial Phonon Transport via Bayesian Optimization
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发表时间：
2016-07
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通讯作者：
S. Ju;T. Shiga;Lei Feng;Z. Hou;Koji Tsuda;J. Shiomi
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作者：
S. Ju;T. Shiga;Lei Feng;Z. Hou;Koji Tsuda;J. Shiomi
我们通过开发一种结合原子格林函数和贝叶斯优化的方法来演示跨纳米结构的热导率优化。为了通过Si/Ge复合界面结构最小化和最大化Si-Si和Si-Ge界面的界面热导（ITC），该方法仅通过计算整个候选结构（超过60,000个结构）的百分之几来确定最佳结构。得到的最优界面结构具有非直观性和冲击性：最小itc结构是一个非周期超晶格，比最佳周期超晶格减少了50%。最小ITC的物理机制可以从两种影响声子输运的交叉角度来理解：随着超晶格层厚度的增加，法布里-珀罗干涉的影响增加，层界面处的反射速率降低。层厚随空间变化的非周期超晶格具有一定的自由度来实现上述两种竞争机制之间的最优平衡。此外，非周期性打破了界面间的建设性声子干涉，抑制了相干声子输运。本研究显示了材料信息学在设计纳米结构以控制热传导方面的有效性和优势，并可推广到其他界面结构。
We demonstrate optimization of thermal conductance across nanostructures by developing a method combining atomistic Green's function and Bayesian optimization. With an aim to minimize and maximize the interfacial thermal conductance (ITC) across Si-Si and Si-Ge interfaces by means of Si/Ge composite interfacial structure, the method identifies the optimal structures from calculations of only a few percent of the entire candidates (over 60,000 structures). The obtained optimal interfacial structures are non-intuitive and impacting: the minimum-ITC structure is an aperiodic superlattice that realizes 50% reduction from the best periodic superlattice. The physical mechanism of the minimum ITC can be understood in terms of crossover of the two effects on phonon transport: as the layer thickness in superlattice increases, the impact of Fabry-Perot interference increases, and the rate of reflection at the layer-interfaces decreases. Aperiodic superlattice with spatial variation in the layer thickness has a degree of freedom to realize optimal balance between the above two competing mechanism. Furthermore, aperiodicity breaks the constructive phonon interference between the interfaces inhibiting the coherent phonon transport. The present work shows the effectiveness and advantage of material informatics in designing nanostructures to control heat conduction, which can be extended to other interfacial structures.