11月14日上午，应我院张晓亮副教授的邀请，德国亚琛工业大学秦光照在能源与动力学院423教室做了题为《晶格热导率的快速准确预测》（Accelerating Evaluation of Converged Lattice Thermal Conductivity）的学术报告。秦光照介绍了第一性原理结合声子玻尔兹曼输运方程求解材料晶格热导率的计算流程，阐述了一种通过快速重建三阶力常数来提高热导率计算速度的方法，并基于电子结构和共振键探讨了长程相互作用力和非简谐性。这次学术报告的开展对我校师生了解微纳米尺度传热领域前沿工作和拓展科研视野具有重要作用，对于我院加强国际交流与合作、进一步推进国际化进程具有重要意义。

报告摘要：

Designing materials with specific properties is a long-term goal in materials science. High-throughputab-initiomaterials screening and design is a new and rapidly growing area in computational materials research. The application of high-throughput calculations has recently made formidable progress and led to novel insights in this field. The lattice thermal conductivity (κ) is a crucial physical property of crystalline materials for enormous practical implications, such as electronic cooling, thermoelectrics, phase change memories,etc. Therefore, the fast evaluation of reliableκfor variety of materials plays a key role in identifying suitable materials for targeted applications. Currently, first-principles based anharmonic lattice dynamics (ALD) method coupled with phonon Boltzmann transport equation (BTE) is one of the most featured methods to obtain theκ, which involves calculation of interatomic force constants (IFCs). Especially, the anharmonic IFCs are evaluated based on the third order derivatives of the total energy with respect to the atomic displacements, which requires huge computational costs. However, severe problem arises for choosing an appropriate (usually not large enough) cutoff distance (r^cutoff) when calculating the anharmonic IFCs. Thus, the high-throughput evaluation of reliableκremains a challenge due to the large resources costs and time-consuming procedures in calculating the anharmonic IFCs for the convergence test.

In this talk, based on the analysis of the harmonic (second order) IFCs, I would like to introduce a concise strategy to efficiently accelerate the evaluation process of obtaining accurate and convergedκby solving the cutoff distance problem. The strategy is efficient for directly determining when theκconverges with respect tor^cutoffand how to fast get satisfactorily convergedκ. With this strategy, we study the divergence problem of thermal conductivity of graphene, a long debate of two-dimensional heat conduction in literature. The feasibility of the method is also confirmed by other systems of phosphorene and bulk SnSe. Insight is obtained from the concept of resonant bonding based on the analysis of electronic structures. In addition, the computing speed with our approach could be one order of magnitude faster compared to the traditional method in most situations, where the ~20^thnearest neighbors are considered. The quantitative strategy proposed herein can be a good candidate for fast evaluating the reliableκand thus provides useful tool for high-throughput materials screening and design with targeted thermal transport properties.

报告人简介：

秦光照现在德国亚琛工业大学（RWTH Aachen University, Germany）从事纳米材料力学性质、电子结构、晶格振动、声子热输运等的第一性原理计算研究，主要关注微纳尺度能量输运问题和热力学性质。截止于17年10月份，总计发表2个Book chapters，2个软件著作权，以及28篇SCI论文，主要发表在Nano Lett., Phys. Rev. B, Nanoscale, Carbon, Appl. Phys. Lett.等知名国际学术期刊，并多次在各种国际学术会议做口头报告。Google Scholar总引用505，h因子为9。