共查询到19条相似文献,搜索用时 78 毫秒
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邵宇飞 《原子与分子物理学报》2016,33(4):736-744
基于晶体的微观结构提出了一种计算晶体宏观弹性应变场的方法,将该方法应用于金属晶体Fe,得到的应变场与连续介质理论预测结果吻合地很好,从而证明了该方法的准确性.以该方法为基础,进一步考虑无限小应变与有限应变的差值,发现应变差值在晶体剧烈变形区域内较强,对金属晶体Cu位错应变场的计算表明这种应变差异可以用来描述位错的运动状态和芯域结构.该方法可为评估晶体缺陷附近应变状态提供依据. 相似文献
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基于平面波法,本论文对应变引起的二维蜂巢晶格光子晶体的能带结构进行了数值计算。选取的两个方向分别是锯齿型边界(zigzag)方向和扶手椅型边界(armchair)方向,在这两个典型方向上对二维蜂巢晶格进行了正负各20%的单轴应变。由于应变导致的对称性破缺,能带结构会有显著的变化。在沿锯齿型边界方向上,TE模带隙随着晶格被拉伸逐渐减小,TM模带隙在应变量大于16%时消失。对于沿扶手椅型边界方向,TE模带隙在压缩15%以上时逐渐减小,在其他应变量的情况下几乎保持不变;TM模带隙在应变量大于18%时消失。这些结果对于完善应力工程和设计二维光子晶体器件有重要的指导意义。 相似文献
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用于微观场小应变测量的云纹干涉载波条纹法 总被引:1,自引:0,他引:1
在云纹干涉法的基础上,研究了一种新的测量方法——云纹干涉载波条纹法,利用初始载波条纹根据物体变形前后的变化对应变进行分析。实验证明:在结合适当的数字图像处理技术情况下,应用频率为1200lp/mm的试件栅,测量试件(微观场)变形产生的应变时,精度基本控制在±10με的范围内。对该方法的研究表明:其灵敏度可在1με以下。方法可给出U场诸行、V场诸列的平均应变值,使研究微观场小应变及微观场临近区域微小应变的不同成为可能。这一技术为MEMS研究中对相关力学内容的分析提供了技术支持。 相似文献
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采用嵌入原子势和分子动力学方法,模拟了单晶铁在一维应变条件下由体心立方(bcc)转变为六角密排(hcp)结构的微观过程. 当应变加载至相变临界值时,hcp相开始均匀形核并沿{011}晶面长大为薄片状体系.弹性常数C31和C32在相变前被逐渐硬化,C33则在相变前出现软化行为;当体系完全相变后,上述各弹性常数显示开始随体积压缩而迅速硬化,温度效应对晶格具有软化作用,可削弱C33的硬化和软化过程;样品在压缩过程可出现孪晶结构,孪晶结构使晶格发生剪切变形.混合相中,hcp相势能比bcc相高,最大剪应力方向与bcc相反向;系统的偏应力与hcp相质量分数近似呈线性关系.
关键词:
结构转变
分子动力学
一维应变 相似文献
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针对刃型位错的滑移运动, 构建包含外力场与晶格原子密度耦合作用的体系自由能密度函数, 建立剪切应变作用体系的晶体相场模型. 模拟了双相双晶体系的位错攀移和滑移运动, 计算了位错滑移的Peierls势垒和滑移速度. 结果表明: 施加较大的剪切应变率作用, 体系能量变化为单调光滑曲线, 位错以恒定速度做连续运动, 具有刚性运动特征; 剪切应变率较小时, 体系能量变化出现周期波动特征, 位错运动是处于低速不连续运动状态, 运动出现周期“颠簸”式滑移运动, 具有黏滞运动特征; 位错启动运动, 存在临界的势垒. 位错启动攀移运动的Peierls势垒要比启动滑移Peierls势垒大几倍. 位错攀移和滑移运动特征与实验结果相符合. 相似文献
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一维光子晶体带隙结构研究 总被引:28,自引:6,他引:22
在考虑介质色散的基础上,研究了介质层厚度对光子晶体带隙结构的影响.利用传输矩阵法,计算了以LiF和Si两种材料组成的一维光子晶体带隙结构.结果表明,介质层厚度的增加会引起禁带的红移,厚度减小会引起蓝移.分析了含空气缺陷层、金属缺陷层的光子晶体结构,发现空气缺陷层对带隙结构的高反射区域变化不大,而在低反射区域,反射系数为零的波带之间出现了两边反射系数增加,中间反射系数减小的情况.在金属缺陷层的带隙结构中,金属对整个波长范围光的吸收作用不同,金属对低反射区1.6 μm、1.85 μm处透射率较大的透射光吸收作用明显,而在1.28~1.38 μm处透射率波长区间,几乎无吸收. 相似文献
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The intra-and intermolecular forces determining the conformation of poly-L-hydroxyproline have been examined. The vacuum conformation of the isolated molecule has the left-hand trans configuration of poly-L-proline II with Ψ = 295°. A second less favorable low-energy form is the right-hand superhelix, also previously described for polyproline. No cis conformation was found to be feasible. Introduction of intermolecular interaction functions shows that the conformation in the solid state is strongly modified to accommodate such interactions. The rotation angle corresponding to the minimum energy in the solid is found to be Ψ = 343°. The crystal structure predicted from these calculations is a hexagonal lattice with a0 = 12.5 Å and c0 = 9.1 Å with space group P32. Three helices are required in the fundamental structural unit. These results are in excellent agreement with X-ray evidence. 相似文献
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本文将等离子体核聚变反应截面研究中利用等离子体环境涨落进行修正了的Debye-Hückel屏蔽势推广到计算等离子体中辐射离子束缚态的能级结构. 通过Tsallis参数q的变化,在等离子体辐射离子束缚态能级结构的计算中加入等离子体参数涨落的平均效应,即,等离子体动力学. 具体给出了利用修正的Debye-Hückel屏蔽势对类氦铝束缚态能级结构的计算结果. 结果表明基于这种修正的屏蔽势,自由电子的极化分布具有和线性Debye-Hückel屏蔽势不同的结构. 这种通过等离子体涨落分布对屏蔽势函数进
关键词:
等离子体中的原子结构
等离子体环境涨落
修正了的Debye-Hückel屏蔽势 相似文献
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An ultracompact refractive index sensing based on the sandwich structure of photonic crystal is presented and demonstrated with solutions of water, methylsilicone and silicone. The performances of the sensor are analyzed theoretically by using Fabry-Perot cavity mode, the change in opposite direction between the transmission of the refractive index sensing and its quality factor is derived. The experimental results are consistent with the results of theoretical analysis. 相似文献
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To understand and develop new nanostructure materials with specific mechanical properties, a good knowledge of the elastic strain response is mandatory. Here we investigate the linear elasticity response in the modified phase-field-crystal(MPFC) model. The results show that two different propagation modes control the elastic interaction length and time, which determine whether the density waves can propagate or not. By quantitatively calculating the strain field, we find that the strain distribution is indeed extremely uniform in case of elasticity. Further, we present a detailed theoretical analysis for the orientation dependence and temperature dependence of shear modulus. The simulation results show that the shear modulus reveals strong anisotropy and the one-mode analysis provides a good guideline for determining elastic shear constants until the system temperature falls below a certain value. 相似文献
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A refractive index (RI) sensor based on the two-dimensional photonic crystal is presented. The sensor is formed by a point-defect resonant cavity in the sandwiched waveguide structure. The transmission spectrums of the sensor with different ambient refractive indices ranging from n = 1.0 to n = 1.6 are calculated. The calculation results show that a change in ambient RI of Δn = 0.001 is apparent, the sensitivity of the sensor (Δλ/Δn) is achieved with 330 nm/RIU (when lattice constant a = 440 nm), where RIU means the refractive index unit; and the transmission efficiency in the RI range of 1.0-1.6 can reach about 40% to 70%, that make the detection of spectrum easy and feasible. The properties of the sensor are analyzed and calculated using the plane-wave expansion (PWE) method and simulated using the finite-difference time-domain (FDTD) method. 相似文献
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Edilson A. Camargo Harold M.H. Chong Richard M. De La Rue 《Photonics and Nanostructures》2004,2(3):207-213
We have fabricated and measured a four-port coupled channel-waveguide device using W1 channel waveguides oriented along ΓK directions in a two-dimensional (2D) hole-based planar photonic crystal (PhC) based on silicon-on-insulator (SOI) waveguide material, at operation wavelengths around 1550 nm. 2D FDTD simulations and experimental results are shown and compared. The structure has been designed using a mode conversion approach, combined with coupled-mode concepts. The overall length of the photonic crystal structure is typically about 39 μm and the structure has been fabricated using a combination of direct-write electron-beam lithography (EBL) and dry-etch processing. Devices were measured using a tunable laser with end-fire coupling into the planar structure. 相似文献
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Y.-G. Han 《Applied physics. B, Lasers and optics》2009,95(2):383-387
We propose a novel and simple scheme for a temperature-insensitive strain measurement by using a birefringent interferometer
configured by a polarization-maintaining photonic crystal fiber (PM-PCF). The wavelength-dependent periodic transmission in
a birefringent interferometer can be achieved by using a PM-PCF between two linear polarizers. Since the PM-PCF is composed
of a single material, such as silica, the peak wavelength shift with temperature variation can be negligible because of the
small amount of the birefringence change of the PM-PCF with temperature change. The measured temperature sensitivity is −0.3 pm/°C.
However, the peak wavelength can be changed by strain because the peak wavelength shift is directly proportion to strain change.
The strain sensitivity is measured to be 1.3 pm/με in a strain range from 0 to 1600 με. The measurement resolution of the
strain is estimated to be 2.1 με. The proposed scheme has advantages of simple structure and low loss without a Sagnac loop,
temperature insensitivity, ease installation, and short length of a sensing probe compared with a conventional PMF-based Sagnac
loop interferometer. 相似文献