基础热物性介电参数是航空航天、太阳能利用等高温辐射换热领域的核心基础参数，是其他工程参数的推算基石；目前高温辐射热物性参数的匮乏，已成为制约高温热辐射研究发展的瓶颈。通过发展第一性原理（第一性原理分子动力学、机器学习势函数）与椭圆偏振实验测量，实现了微波-红外-可见光-紫外光谱波段高温介电参数的准确预测，进而为航空航天、高温透波、雷达隐身、太阳能利用等领域高温辐射换热工程应用研究提供基础数据支撑。

高温介电参数的研究围绕以下几个方向展开:

(1) 椭圆偏振光谱仪实验测量

     从美国J.A. Woollam公司购置了RC2和IR-VASE Mark II椭偏偏振仪，实现0.2-30 um光谱波段、-70-600℃温度范围介电参数的实验测量。

(2) 微波介电参数深度学习分子动力学模拟

提出了一种准确计算氮化物基高温透波材料微波介电函数的计算方法，其技术特点是基于第一性原理分子动力学，计算出不同温度条件下原子的轨迹，受力以及能量信息。然后，结合深度神经网络对原子能量，位移和受力信息进行训练拟合出高温下的深度学习势。最后，基于深度学习势进行分子动力学模拟计算得到偶极矩信息，然后基于线性响应理论对体系偶极矩的自相关函数进行傅里叶变换得到极化弛豫时间，进而应用柯尔-柯尔（Cole-Cole）公式计算得到氮化物透波材料的介电函数。

深度学习分子动力学方法计算微波介电参数技术路线

(3) 红外介电参数第一性原理分子动力学模拟

       红外波段，光吸收主要源于入射光电场与声子（晶格振动量子化描述）间的耦合作用。根据黄昆-玻恩理论，当电磁波在介质中传输时，晶格振动产生的光学支声子与光子产生耦合作用。该耦合机理可通过双原子线性链条模型进行描述。

双原子线性链条模型

(4) 可见光-超紫外介电参数第一性原理模拟

       可见光-超紫外波段，入射光子引发电子在不同能级间的跃迁，伴随着光子的吸收或发射。当入射光子的能量ћω大于禁带宽度Eg时，价带内电子将跃迁至导带，并在价带内产生自由移动的空穴。伴随着电子向高能级态激发的同时，高能级态电子向低能级态跃迁，在跃迁过程中将释放光子。

电子能级跃迁示意图

相关研究成果：

[20]  S. Zhang, T. Fei, T. Cheng, J. Y. Yang* and L. Liu. Temperature-dependent UV-Vis dielectric functions of BaTiO3 across ferroelectric-paraelectric phase transition, Opt. Express 31 (8), 12357-12366 (2023).

[19]   杨家跃，成涛，费天皓，刘林华. 一种宽温域介电常数的无损光学测试方法及系统. 发明专利（已受理）

[18]   Z. Li, X. Tan, X. Duan, J. Zhang, J. Y. Yang*. Deep learning molecular dynamics study on microwave high-temperature dielectric function of silicon nitride, Acta Phys. Sinica, 24 (2022).

[17]    W. Zhang, Z. Zeng, T. Cheng, T. Fei, Z. Fu, X. Liu, J. Zhang, J. Y. Yang*. Finite Temperature Ultraviolet-Visible Dielectric Functions of Tantalum Pentoxide: A Combined Spectroscopic Ellipsometry and First-Principles Study, Photonics, 9(7), 440 (2022).

[16]   T. Fei, T. Cheng, H. Zhao, L. Zhang, X. Xie, Z. Fu, J. Y. Yang*, L. Liu*. Temperature-sensitive hybridization of propagating and localized surface phonon polaritons in polar 4H-SiC nano-resonators, J. Appl. Phys., 132, 123101 (2022).

[15]   Q. Li, G. Liu, J. Yu, G. Wang*, S. Wang, T. Cheng, C. Chen, J. Y. Yang*, X. Xu, L. Zhang*. A perovskite/porous GaN crystal hybrid structure for ultrahigh sensitivity ultraviolet photodetectors, J. Mater. Chem. C, DOI: 10.1039/d2tc01207c.

[14]  T. Fei, T. Cheng, L. Zhang, J. Zhang, J. Y. Yang*, L. Liu*. Temperature-dependent infrared dielectric functions and hybrid phonon-polaritons in wurtzite GaN: A spectroscopic ellipsometry and multiscale simulation study, J. Appl. Phys., 131, 093102 (2022).

[13]  J. Y. Yang*, T. Cheng, T. H. Fei, C. Zhang, L. Liu*. Temperature-induced surface phonon polaritons dissipation in perovskite SrTiO₃. Opt. Lett., 46(17): 4244-4247 (2021).

[12]  T. Cheng, T. H. Fei, W. J. Zhang, J. Y. Yang*, L. Liu*. Ellipsometric and first-principles study on temperature-dependent UV–Vis dielectric functions of GaN. Appl. Opt., 60(23): 6869-6877 (2021).

[11]  W. J. Zhang, T. H. Fei, T. Cheng, C. Zheng, Y. B. Dong, J. Y. Yang*, L. Liu*. Doping and temperature-dependent UV-Vis optical constants of cubic SrTiO3: a combined spectroscopic ellipsometry and first-principles Study. Opt. Mater. Express, 11(3): 895-904 (2021).

[10]  M. Xu, J. Y. Yang and L. H. Liu*. Temperature-dependent dielectric functions of bcc transition metals Cr, Mo, and W from ultraviolet to infrared regions: A theoretical and experimental study, J. Appl. Phys., 123 (15), 155102 (2018).

[9]   J. Y. Yang and M. Hu*. Temperature-Induced Large Broadening and Blue Shift in the Electronic Band Structure and Optical Absorption of Methylammonium Lead Iodide Perovskite, J. Phys. Chem. Lett., 8, 3720 (2017).

[8]   M. Xu, J. Y. Yang, S. Y. Zhang and L. H. Liu*. Role of electron-phonon coupling in finite-temperature dielectric functions of Au, Ag, and Cu, Phys. Rev. B, 96, 115154 (2017).

[7]   J. Y. Yang, M. Xu and L. H. Liu*. Infrared Radiative Properties of Alumina up to the Melting Point: A First-Principles Study. J. Quant. Spectrosc. Radiat. Transf. 184:111-117 (2016).

[6]  J. Y. Yang and L. H. Liu*. Effects of Interlayer Screening and Temperature on Dielectric Functions of Graphene by First-Principles. J. Appl. Phys., 120. 034305 (2016).

[5]  J. Y. Yang and L. H. Liu*. Temperature-Dependent Dielectric Functions in Atomically Thin Graphene, Silicene and Arsenene, Appl. Phys. Lett., 107, 091902 (2015).

[4]  J. Y. Yang, L. H. Liu* and J. Y. Tan. First-Principles Study on Dielectric Function of lsolated and Bundled Carbon Nanotubes, J. Quant. Spectrosc. Radiat Transf., 158: 78-83(2015).

[3]  J. Y. Yang, W. J. Zhang, L. H. Liu*, J. Qiu, K. Wang and J. Y. Tan. Temperature Dependent Infrared Dielectric Functions of MgO crystal: An Ellipsometry and First-Principles Molecular Dynamics Study, J. Chem. Phys., 141(10): 104703 (2014). 

[2]   J. Y. Yang, L. H. Liu* and J. Y. Tan. Temperature-Dependent Dielectric Function of Germanium in the UV-Vis Spectral Range: A First-Principles Study, J. Quant. Spectrosc. Radiat. Transf., 141: 24-30 (2014).

[1]   J. Y. Yang, L. H. Liu* and J. Y. Tan. First-Principles Molecular Dynamics Study on Temperature-Dependent Dielectric Function of Bulk 3C and 6H SiC in the Energy Range 3-8 eV, Phys. B: Condens. Matt., 436: 182- 187 (2014)