过渡金属化合物OsB2与OsO2低压缩性的第一性原理计算研究

利用基于密度泛函理论平面波赝势法的第一性原理计算,研究了过渡金属化合物OsB2和OsO2的金红石相、黄铁矿相与萤石相三种结构在高压下的状态方程和结构特性以及OsO2可能的高压相变.理论计算结果支持OsB2与OsO2的萤石相是潜在超低可压缩性的硬性材料.同时,也分析了它们的电子结构,力求理解大体变模量和高硬度的微观机制.结果表明,可以利用过渡金属高的价电子浓度,掺入硼、氧、碳、氮等轻的元素形成强的方向键,这可能提供了一种合成超硬材料的新途径.     

Nano liquid-metal fluid as ultimate coolant

We proposed for the first time the concept of the nano liquid-metal fluid, aiming to establish an engineering route to make the highest conductive coolant. Using several widely accepted theoretical models for characterizing the nano fluid, the thermal conductivity enhancement of the liquid-metal fluid due to addition of more conductive nano particles was predicted. Further, the effects of particle size, cluster of nano particle, solid-like layer due to adsorption, volume fraction and particle types were evaluated. Having the highest conductivity, being electromagnetically drivable, the liquid metal with low melting point is expected to be an idealistic base fluid for making super conductive solution which may lead to the ultimate coolant in a wide variety of heat transfer enhancement area.     

Influence of Interorbital Interference on Tunneling Process in STM

We present a theoretical study of the influence of intra-atomic interorbital interference on the formation of STM images of metal surfaces. The obtained results show that this kind of interference may modify significantly the tunneling current by the increase or decrease of the current contributions flowing through different orbitals of the surface atoms. STM simulations performed for aluminium and nickel surfaces indicate that the height of corrugation and the topographies of STM images of different surfaces depend considerably on this interference.     

基于亚微米光栅透射共振蛋白质检测模型研究

建立了一种基于亚微米光栅透射共振理论的蛋白质检测模型,设计了一种金属光栅型蛋白质检测生物传感器,运用光栅耦合激发表面等离子体共振理论对提出的模型进行了理论分析,通过计算机计算模拟,分析了蛋白质样品折射率、厚度等对透射率的影响。结果表明:透射率与样品折射率、厚度呈二阶多项式关系,并且厚度、折射率都随灵敏度的增加而增加。这种检测模型可应用在蛋白质检测传感方面。基于此方法的蛋白质检测模型具有同时检测蛋白质种类和含量、灵敏度高、实时、无需标记,便于集成芯片化,适用于批量生产、成本低等优点,在蛋白质芯片、生物分析、环境监测、生物器件研发等方面具有广泛的应用前景。     

金属薄膜制备及物性测量系列实验

介绍了由模拟真空实验和“金属薄膜的制备”、“金属薄膜厚度的测量”、“金属薄膜电阻率的测量”,以及“金属薄膜生长过程的动态监测”等4个实验组成的金属薄膜制备与物性测量系列实验.这组实验与现代科学技术发展联系紧密,仪器设备可靠,操作简单,适合于普通物理实验阶段的研究性教学.     

二维非正交坐标斜方格金属光子带隙结构

金属光子带隙结构在高能加速器、微波真空电子器件和太赫兹波源等方面具有重要的应用前景.基于实空间传输矩阵理论，详细研究了非正交坐标系下二维斜方格金属光子带隙结构，给出了计算横电模、横磁模完全带隙结构的一般公式，并分析了填充系数、任意斜角及金属柱横截面对带隙结构的影响.计算结果在退化为正方格情况下时，与其他方法的计算结果取得很好的一致. 关键词： 光子晶体 金属光子带隙 传输矩阵法 微波真空电子器件     

Pt(110)表面自吸附原子能量和力的改进分析型嵌入原子法分析

采用改进分析型嵌入原子法计算了Pt(110)表面自吸附原子的能量和法向力.当Pt吸附原子位于Pt(110)表面第一层原子的二重对称洞位上0.11nm时最稳定.Pt吸附原子的最佳迁移路径是由一个二重对称洞位沿密排方向迁移到最近邻的另一个二重对称洞位.在吸附原子远离表面的过程中，将依次经过排斥、过渡和吸引等三个区域.在排斥区和过渡区，由于吸附原子与表面原子间强的相互作用势，吸附原子的能量和法向力的形貌图均为(110)面原子排列的复形，与对势理论和嵌入原子法得到的结果一致.在吸引区，由于多体相互作用及晶体中原子 关键词： 金属表面 自吸附 能量 力     

Anisotropic thermoelectric and superconducting properties of the bulk misfit-layered (SnSe)1.17(TaSe2) compound

We present the thermoelectric and superconducting properties of the bulk misfit-layered (SnSe)_1.17(TaSe₂) compound with the critical temperature (T_c ~ 3.8 K). From XRD and electrical resistivity, the anisotropic properties of the misfit-layered compound by the preferred orientation were observed. The zero-temperature-limit upper critical field H_c2(0) and coherence length ξ are obtained by H_c2(0) = 8.94 T and ξ = 6.1 nm. The electron-phonon coupling constant (λ_e-p = 0.735) and the specific heat jump (ΔC_e/γT_c ~ 1.4) imply that the (SnSe)_1.17(TaSe₂) compound is a weak coupled conventional s-wave superconductor. Density functional theory (DFT) calculation results show that some electronic charge transfers from the SnSe layers into the TaSe₂ layers. In addition, the thermoelectric properties of the bulk misfit-layered (SnSe)_1.17(TaSe₂) compound show significant anisotropic properties.     

Prediction of Liner Metal Temperature of an Aeroengine Combustor with Multi-Physics Scale-Resolving CFD

Computational Fluid Dynamics is a fundamental tool to simulate the flow field and the multi-physics nature of the phenomena involved in gas turbine combustors, supporting their design since the very preliminary phases. Standard steady state RANS turbulence models provide a reasonable prediction, despite some well-known limitations in reproducing the turbulent mixing in highly unsteady flows. Their affordable cost is ideal in the preliminary design steps, whereas, in the detailed phase of the design process, turbulence scale-resolving methods (such as LES or similar approaches) can be preferred to significantly improve the accuracy. Despite that, in dealing with multi-physics and multi-scale problems, as for Conjugate Heat Transfer (CHT) in presence of radiation, transient approaches are not always affordable and appropriate numerical treatments are necessary to properly account for the huge range of characteristics scales in space and time that occur when turbulence is resolved and heat conduction is simulated contextually. The present work describes an innovative methodology to perform CHT simulations accounting for multi-physics and multi-scale problems. Such methodology, named U-THERM3D, is applied for the metal temperature prediction of an annular aeroengine lean burn combustor. The theoretical formulations of the tool are described, together with its numerical implementation in the commercial CFD code ANSYS Fluent. The proposed approach is based on a time de-synchronization of the involved time dependent physics permitting to significantly speed up the calculation with respect to fully coupled strategy, preserving at the same time the effect of unsteady heat transfer on the final time averaged predicted metal temperature. The results of some preliminary assessment tests of its consistency and accuracy are reported before showing its exploitation on the real combustor. The results are compared against steady-state calculations and experimental data obtained by full annular tests at real scale conditions. The work confirms the importance of high-fidelity CFD approaches for the aerothermal prediction of liner metal temperature.     

Polarized photoluminescence spectroscopy in WS2, WSe2 atomic layers and heterostructures by cylindrical vector beams

Due to the large exciton binding energy, two-dimensional (2D) transition metal dichalcogenides (TMDCs) provide an ideal platform for studying excitonic states and related photonics and optoelectronics. Polarization states lead to distinct light-matter interactions which are of great importance for device applications. In this work, we study polarized photoluminescence spectra from intralayer exciton and indirect exciton in WS₂ and WSe₂ atomic layers, and interlayer exciton in WS₂/WSe₂ heterostructures by radially and azimuthally polarized cylindrical vector laser beams. We demonstrated the same in-plane and out-of-plane polarization behavior from the intralayer and indirect exciton. Moreover, with these two laser modes, we obtained interlayer exciton in WS₂/WSe₂ heterostructures with stronger out-of-plane polarization, due to the formation of vertical electric dipole moment.